For what it's worth, I got my sounds back in Windows 10 on my interface. I unplugged the USB 3 connection to the zoom UAC-2 on the computer (as the manual says!) then uninstalled the drivers for the Zoom UAC-2 audio interface and the Zoom software, as well as any other audio drivers Windows would let me zap. Then I rebooted and re-installed the Zoom software and rebooted. Then connected the Zoom USB 3 connection, switched it on and rebooted the computer. All working fine again. I just hope tonight when I switch the PC back on it still all works. I've got harmonies and guitar coming in stereo to the zoom via a Voicelive 2 vocal processor which the zoom mixes with the BIAB backing tracks via its loopback function. Good sound. Just need to tweak the Voicelive 2 as a find it a bit overbearing and some of the settings are less than practical. I drive the harmonies from an acoustic guitar although previously I drove the harmonies via midi from BIAB which also worked well. The Zoom has a midi interface as well as the two audio interfaces, so it's pretty straightforward. Live I'll probably drive the voice live from guitar or mp3.

Windows 10 Home 20H2 Build 19042.487
BIAB 2021 (Build 818)
Intel(R) Core(TM), i3-4160, CPU @3.60 GHz RAM 16 GB, 64 Bit X64-based processor
Zoom UAC-2 (USB 3 interface-built in midi)
VoiceLive 3 Extreme, Sputnik Valve Condenser Mic