I am also interested in buying a new compact android phone, as I am still on my Motorola Moto X4 (2017.. that will be 6 years in September). The ZF10 seems interesting, but there have been some complaints about the camera from some reviewers (without going more into detail).
I wonder if the same problems exists, if you use a third-party camera-app. There are many options in the Google Play Store. Maybe only the stock-camera-app doesn't work that well, and maybe with some third-party apps the user can adjust certain settings to improve the taken photos? Do the camera photos differ between stock Android and Zen UI on top? Or is this just impossible, because e.g. the ghosting issues are ingrained in the hardware/firmware?
On a side note: I use a mirrorless camera for taking photos and videos, so the camera functionality on the ZF10 wouldn't be my biggest concern.
It's hard to tell if the same problems exist in other apps. Some apps work differently and don't have all the configurations of the Asus camera app (like auto ISO, for example). Other apps can process normal photos differently, but I think it's a matter of finding out.
In my experience with Zen9, the best third-party app out there is the OpenCamera, but still far away from having a good UX. I also use it because it delivers RAW files, while the Asus doesn't.