The Nikon Z6III has a very interesting sensor, that works with either a mechanical and/or electronic shutter depending on the situation, and which reads the image very quickly, allowing for a high number of shots per second and high framerate videos. The quality of the image is very good, too (I'd recommend sticking with the S lenses). It comes with a very capable In-Body Image Stabilization, but more on that later, and an impressive viewfinder.
The settings are quite exhaustive, though they removed a few functionalities of the Z9 just because it's a mid-range product, which leaves a bitter after-taste. I'm pretty happy with the possibilities, though it requires some getting-used-to before finding an option in the menu system. The customization is fair, but I'm missing a few options, and also a few more buttons for shortcuts.
There's something a little unsettling with the IBIS: the Z6III makes a loud sound each time the user enters or exits the menu, each time the device is switched on or off, and each time it goes in and out of idle mode (which happens a lot). It defeats the silent mode for special events, and I'm a little concerned it would artificially wear down the mechanical system. It's not a defect of my camera; I've seen that reported a few times by reviewers and users alike. It looks like a firmware issue.
I tried to contact the support about it, and that's what revealed my 2nd-biggest problem with the product: the complete lack of support. They played dumb with that issue, even after I provided them with a simple step-by-step procedure for them to understand and experience it first-hand. Since then, they've refused to answer me any further about that specific issue.
I contacted them for a few other things, like a software that had just mysteriously disappeared from their website, making it impossible to use the custom control picture feature, and they were vague and unhelpful, too. Their support is like a brickwall isolating customers from a more competent technical support line. At this price, it's unforgivable.
Cheap was also the feeling when, at this price tag, you don't even get a proper battery charger nor a printed manual (the small starting guide doesn't count, unless you've never used a camera before). They sell the charger separately, but the price is ridiculously exaggerated for what it is. The camera also comes with the shortest USB cable I've ever seen; I strongly recommend buying a normal-sized cable if you want to connect to the Z6III to charge its battery or to extract the images - though a card reader will avoid depleting the battery, and is thus recommended, too.
Talking about the battery, it doesn't last too long, so better to have two of them.
I really like the new compressed raw format the Z6III inherited from the Z9, NEF HE. It saves half the size without noticeably altering the quality; that's a very good job. The NX Studio is probably the best tool to take advantage of it, since tools like Affinity, Darktable, or Rawtherapy won't get quite the same sharpness out of some raw shots and won't reapply the post-processing. Note also that many programs don't support the compressed raw, so you may have to use Adobe's free DNG converter first, but be aware that it drops some of the metadata. Unfortunately, I haven't found any tool to convert compressed NEFs into uncompressed NEFs, which would have avoided the issue since those can be read by most software. I don't know the status with Adobe's extravagantly expensive paid tools, so I can't comment on them; my educated guess is they suffer from the same limitation as their converter (there have been rumours of them dropping the support for Nikon's NEF format, too, maybe because Nikon acquired RED).
So, overall: great and innovative hardware, good but perfectible ergonomics, sub-standard to inexistent support, and falls a little short when it comes to what's in the box.
NOTE: This website forces me to give a score to robustness, though it's too early for me to judge. Disregard that score.