The new ZS10 model by KZ was received well by KZ fans, but issues were pointed out as well. While maintaining an excellent standard for sound quality, at least once you got used to the intrusive upper-mids, they messed up the design quite a bit. The housings are huge, and the short nozzle alongside a bulge right after it, makes those earphones a difficult fit, despite the fact that a perfect fit is mandatory in order to experience the intended bass response.
With all that in mind, these earphones are excellent, but if given a choice between these vs. ZS6, I vouch for ZS6.
Comfort is a mixed bag. Thanks to the new cable they are very easy to put inside, but you won't likely to get a proper fit. It's not due to wide nozzles. In fact, the issue seems to be linked to the fact that the nozzles are very short, and where the nozzle ends there's a bulge that puts pressure against my ear canals and actually makes me feel uncomfortable after a while. That bulge is just too wide to fit in my ears. Giving up on the bulge and making the nozzle longer would have easily prevented this. One more thing to note is that the housings are very large and bulky. No matter what you do, they will always stick out. Have small ears? That might be a problem.
Lows / Bass
The bass quantity really depends on how well to manage to fit these earphones in your ears. The thing is, that these earphones have a bass vent (just like ZS5 and ZS6), and in order to get the best bass experience, the fit has to be perfect, and your ear is supposed to cover up the vent, else the bass will seem thin. Overall, the bass isn't all that different than ZS5, I can barely tell the difference. It's well-balanced, mildly warm and not muddy at all, yet quite impactful and gets very deep. While not necessarily basshead-material, it's the kind of bass that most people can appreciate.
Mids / Vocals
The mids maintain a great sound quality, like KZ's previous flagship models, but with the ZS10 they seem to be more intrusive and in-your-face, possibly due to a significant peak in the upper-mids range. At the same time, the lower-mids seem to be slightly subdued, which results in a colder tone, especially on vocals.
Highs / Treble
Extremely detailed treble, without having any intrusive peaks anywhere in the sibilance or pierce regions. The treble is bright and crisp and instruments are really well-separated. However, they will definitely be too fatiguing for some listeners, mainly due to bright and intrusive lower-treble/upper-mids combined with relatively subdued lower-mids, which adds up to a brightly colored tibre overall.