Hi folks,
used a couple of hours this weekend to get Volumio on a Pi Zero running. The first tries ended up in the device entering “emergency mode” 
My guess: The zero has not enough RAM to startup a “fresh-flashed” image ?
My solution: Putting the “fresh” SD (4 Gb seems to be enough) in my other Pi (3B+) 
and let him do all the configuration stuff. Voila: The SD also works with the zero.
This information may be useful for someone.