Disclaimer: Long ramble.
I see that KZ products are not marketed well. So you either stumble upon these amazing products or some stoked friend recommends them. I gambled first on a pair of KZ ZS 10 pro and was immediately blown away by what it has to offer. And gradually I realised it is somewhat for the bass heads(but with no compromise on the other frequency range). I gifted it to my wife who was super happy with them as she loves it's thump. I shifted to KZ ZSX. And I am hooked. I was looking for a true wireless earplug in the market, for taking calls on the move in this pandemic time. And stumbled on KZ AZ09(not KZ AZ09 Pro). Again another KZ. I gambled again. The experience was mixed. I was extremely happy with the audio quality of music or movies. But it had two major significant issues. One, it is uncomfortable where it wraps around your ears, especially, during long duration usage. And second it's mic was of very poor quality. The person on the other end of the call could hardly hear me. The second point failed the most primary requirement(calls). And the third reason, not very frequent though is connection loss for fraction of a second when you are on a bike. Specially while taking turns or turning your head left or right. So long story short I was disappointed partially. For calls, I went back to using the cable that came along with the IEM. And then I stumbled upon these, the subject of the review :). Fortunately enough these didn't exist when I ordered the KZ AZ09. Otherwise I would have hit myself on the face for insufficient research. So I gamble on the KZ AZ09 Pro. This was a super risk because as it was new there weren't many reviews on the net. People spoke about the enhanced comfort but nobody compared the mic with the predecessor. Still I put my buck in it. Thanks to HeadphoneZone, I got it at half the price compared to Amazon. Because Amazon ran out of domestic stock and was importing it to India at more that double the price. And on top of all this I got some amazing playlists card that was HedphoneZone exclusive :). So coming to the main points after the long rant. These bluetooth upgrade cable are the best out there in the market unanimously. 
Pros
1. They are modular ie. pair them with any IEM that favors your tuning preference.
2. They are super comfortable
3. They are very secure. Will never fall even if, you are an acrobat.
4. They are to some extent discrete too, specially if you have long hair that covers your hair :). 
5. The mic is better that the apple wireless airpods and equally good as the current version.

Cons
1. No volume control. Which is not an issue with me. But I am sure some of you out there will miss that. I however use Siri for volume control, if my phone is buried in my jacket pocket.

It has been around 15 days since I got these delivered and I am already facing issues, I was very sceptical at first since reviews for AZ09 non-pro were really bad, it had disconnection issues and whole lots of problems. After that AZ09 Pro launched and it was very hard to find reviews for it, do you believe that no one really bought these?

So coming to my review, the unit has started malfunctioning in the first 15 days and the return window is closed.
The problem: As soon as I turn on the Bluetooth of my phone or laptop the AZ09 pro instantly connects even if the lid of the case is closed and music starts playing while the lid is on, I have to manually turn off the Bluetooth or pause the music. While I am listening to music and putting them in the case, music doesn't stop either it continues playing 🤣🤣🤣 f*l . Also sometimes it stutters and skips.....great!!! that's what I wanted.

The ticket support system doesn't have KZ in the list so I can't submit a support ticket, the return button is removed from the orders page so now I can't do that either.

The warranty page for KZ on the headphone zone website says this: "Once your claim request is approved, a unique WCID (Warranty Case Id) number will be issued to your case. Once it's approved, the faulty unit has to be couriered to us by the customer."
Just great, after sending the unit to them at my expense, they might send me a working one if they have one in stock.😥☠️

I am using these with KZ ZSN Pro X, was planning to upgrade to KZ CRN or something else but I think there is no need for that. I don't think these TWS will be alive for that long.
BTW It has a Type-C port for charging, the case is a chonker like double the size of a normal TWS, you can't have anything else in your pocket after putting these in.
The connection is fast and seamless, and the sound quality is quite good (my phone supports aptX, your mileage may vary.) The Battery is okay, and the audio quality during calls is okay, but you have speak louder than normal so the person on another side can hear you properly. I was not able to connect 2 devices at the same time, it worked for some people idk.

I hope the headphone zone team resolves this issue somehow or I just wasted 3.5k for nothing.

Hi,

I purchased this TWS in the month of Feb 2022 and within 1 month unit started giving trouble.

1. Mic was not working (this was with mic model) from beginning
2. After 3 weeks, only right ear piece was getting connected and left ear piece continuously blinks blue light without connecting
3. I can connect either one ear piece at a time not both

I had put trust in Headphone zone and bought this product and really not happy with this.

Few months back I was thinking what if we could turn our TWS into wired earphones, and wondered if a similar technology existed. That time, I wasn't aware that something like IEMs with pin connectors already existed. But when I stumbled upon Shure - AONIC 215 True Wireless Gen 2, I was amazed, it was like a dream come true. Sadly the dream was crushed by the high price. Few weeks later, found out about AZ09 Pro. Only problem, I owned Moondrop SSR, which have B-pin connectors, while these are only available with C-Pin for now (B-Pin model exists but not available currently). So I reached out to Headphone Zone, and decided to buy KZ - ZS10 Pro as per their recommendation. Obviously, you have to buy a pair of IEMs separately and this is a barebone adaptor. This will turn your wired IEMs in TWS. Now let's talk about a few things to note -

1) The audio quality and performance might differ based on the technologies your device supports. My phone has Snapdragon 730, some sites say it supports aptX HD but Qualcomm's product page has no mention of aptX HD, only aptX Adaptive. But again, Qualcomm doesn't mention anything about aptX HD even in Product Page for Snapdragon 8 Gen 1. It seems that Qualcomm replaced aptX HD with aptX adaptive for all new devices, which supports bitrate ranging from 276 - 420 kbps compared to 570 kbps in aptX HD. Qualcomm also has aptX Lossless, but good luck finding any TWS with it for now.

2) Though both my phone and macbook support bluetooth 5.0, I would notice momentarily latency increase on my macbook from time to time (sound would become choppy, disappear). This could be either due to my mac running too many apps and connect to an external 4k display, and thus running hot or the fact that a mouse and keyboard are also connected.

3) This supports AptX/AAC/SBC, not LDAC. LDAC is not mentioned anywhere in description, so don't assume it's a given. There might be some noticeable difference in quality when using your IEMs wired and with these wireless adaptors.

4) Case is on the chonkier side. It won't fit that easily in your pockets, unless you have very large pockets.

5) Switching between devices might not feel as convenient. You have to disconnect them from the device they are currently connected to, to able to connect with another device.

6) Volume control support not given. Also the click actions are not re-configurable.

If these things don't bother you, go with them. Personally, most of the points I mentioned are not a bother for me. Though I wished they gave volume control in place of voice assistant, since my assistant is voice activated anyway. You can use a 3rd party app to remap them on android, but it would be cool to remap them across all devices. Also I wished the case was slimmer, but I think they did it in order to fit atleast all KZ IEMs in the case. Still happy with what they offer for the price. Hope in next iterations they'll improve upon these things.

PS: They come into pairing mode as soon as you disconnect them from your device. This is convenient to quickly pair a new device, which most TWS miss on.

If you have Type C PIN IEMs and need an inexpensive route to TWS then KZ AZ209Pro are definitely worth a try.
The earhooks fit great around the ears and also are very light hence wearing them for an extended period of time would'nt be an issue.
They are just Sweat proof according to KZ's site, hence the usecases for these would have to be based on that.

The rubber'ish material around the earhook should last maybe for 1 year post which they may deteriorate depending upon the climatic condition.
Anyways for the price that they currently retail at and given the fact that most TWSs don't last beyond 1-2 years they still are a bang for the buck considering even if they conk off there is always a workable pair of IEMs left out or vice versa.

Coming to the sound which also depends on the IEMs they are paired to, they sound good. Don't expect Wired level of quality but these are competent enough to match upto 80% of it w.r.t wired quality or i'ld put it this way they are more than enough for day to day streaming apps like Spotify (@very high streaming quality settings). These support AptX hence the Battery drain, Processing load and Sound quality 'In Theory' should be somewhat better . I use them with AptX mode and to be honest my listening sessions don't extend more than 3 hours a day in total on earphones/these, so for me the battery has lasted a week as of now ( it has been just 7-9 days since I got them) with the Charging case (which has been charged just once).
Coming to connectivity part, haven't faced any consistent/intermittent connectivity issues as such and have only faced 1-2 times connectivity/sync issues but it lasted only maybe for a nanosecond or so and they reconnected back, not sure whether it was due to interference from other bluetooth devices around it.
I would say these have very good connectivity (based on my usage till now), the range is also acceptable (atleast 5-10meters and a couple of walls) and the pairing is very fast.

These do have a tiny noise floor which may not be distracting once the music starts playing but its definitely there if you look for it ( I guess most TWSs do have that atleast the budget ones)
Microphone quality is nothing to write about and they are below average at best.
The charging case has a decent build quality and needs to be slow charged (KZ is very particular about it) and is chonky and an average person wearing jeans won't be able to carry it in their pockets.

Overall (assuming if these last for aleast 1 year) i'ld say go for these as they don't burn a hole in your pocket but at the same time sound quite good and would be worth the money spent.

Earphones tested with: KZ ZSN Pro & KZ DQ6

Quality impression: Seems decent. Allthough ZSN Pro seems louder than the DQ6 at the same volume.

Feature Impression: The single earbud usage feature is a godsent. The switching is very seamless. I tested it during calls, and the caller couldn't even tell I switched from the left to the right. But yeah with both the earbuds being used, the noise cancellation comes into effect and the voice clarity improves slightly.

Battery Life Impression: I have been using the earbuds after fully charging the case with the earbuds in it to 100% and now the earbuds are being used constantly (calls + music + movies) from 3 PM and now its 7:30 PM, and my laptop reports the battery of the earbuds to be at 70% battery remaining (it dropped in 10% intervals).

Others: My samsung phone picks up AptX straight up and poweramp plays back at 24 bit 96 KHz. Quality is very good compared to any other bluetooth earphone at this range. Pairing and device switching is seamless but you have to disconnect the earphones from the device or try to connect from the device directly for better results. ( I have paired it with my phone and laptop and I can switch as I like). I also like that this has contact charging instead of wireless, it increases energy efficiency yet so slightly (I am an Electrical Engineer, I know what I am talking about). Haven't tested the high performance mode yet.

The value is absolutely amazing! Got this with the kz crn and it is mind-blowing over bluetooth too. Packs a lot of punch.
It is a chonkster tho(refer image for reference)