3rd-party streaming apps on the ZX507 have two options, via the Sony audio setting “Hi-Res Streaming”: when set to On, all audio from 3rd-party apps is upscaled to 32b/192kHz; when set to Off, all music is passed to the Android audio mixer and resampled to 16b/48kHz.
The latest version of USB Audio Player Pro (UAPP) will detect the hi-res-capable internal DAC of the ZX507 now and bypass Android audio (and the “High-Res Streaming” On/Off 32b/192k SRC setting) and output bit-perfect. That’s the only 3rd-party app that will bypass the Android audio stack currently.
The native Walkman Music app for local music is bit-perfect though.