A few thoughts after a few weeks with the ZX507...
Set up: Qobuz/UAPP/SD card with FLAC library (16/44 and 24/96/192), 4.4 balanced Fiio cable, Westone W80 iems, spinfit eartips.
First and foremost, this is a hedgehog DAP rather than a fox - it does one thing very well, in every other respect there are some compromises.
If you use files stored on the device, played through the stock app, using 200+ hour burned in balanced output to decent iems or headphones, the 507 is an absolute marvel. SQ is fantastic across a range of genres, preferable (IMHO) to direct competitors like the A&K SR25 and to numerous 'high end' portable usb-DACs that I've tried (L&P W2, Lotoo Paw S1 and S2, A&K Pee51, Hidisz s9 Pro, etc.). Used this way battery life is respectable, at easily 14-16 hours. The tiny form factor is also a real boon as you are likely to be carrying two devices.
If used in any other way there are compromises, which, as observed in this thread, mostly come from battery life and android resampling. If you play local files through UAPP, avoiding resampling, then battery life is about halved (brighter sound signature - still very nice). If you stream through UAPP then battery life is even worse. Maybe 4 or 5 hours. If you use the Qobuz (or any other) app then not only is battery life poor, but you also get everything resampled, significantly reducing SQ.
The good news for me is that 90% of the time I play locally stored files. If you want to use android apps or to stream your music, I'd suggest you look elsewhere. In sum, the 507 is, fundamentally, a fantastic high-res old-school iPod, doing one job really well, and as such compromised beyond that (though it's nice to have those options).
Not sure any of this is news to anyone, but just thought I'd add to the picture.