This may technically work, though the switch would not get its own dedicated LPSU rail, but take the 5V from the the overall motherboard which yes will have a low noise floor. However, you need to consider the sheer amount of noise that switch may be injecting back in to the ZENith. Therefore, you can give it a try and make your own listening tests and assessments.
Feeling adventurous, I've hooked up my Chord EE8 switch to my Zen 3's USB port. Overall sound quality does seem better vs. the iFi X supply I was using (which in turn was a slight improvement over the 5V supply that came with the switch).
As noted above, no dedicated rail, but perhaps still some gains from the Zen's low-noise PS? I'd assume the EE8 is sufficiently well constructed not to inject anything nasty back into the Zen.
