Resume:
The raspiaudio Hat works flawlessly with a RPi Zero W. It work like a Hifiberry clone.
Only drawback, that is also true for majority of Pi Hat no native soft volume control. Lots of user found several ways to get it modifying the RPi config like the link I gave but it doesn’t seems to work with M2P…
I would recommend you try contacting the manufacturer of your sound card and inquire whether such an implementation would be possible with the card and what it would take as we are not intimately familiar with the product.