Sorry about the confusion.
All players (your zero’s, too) connected to the LMS with shairtunes2 on it automatically turn into AirPlay devices.
Make sure you only have the shairtunes2 (fork) plugin active and no other plugins called shairtunes in the LMS settings.
The IP in shairport is for an automatic switch between Squeezelite and shairport. So if you want to use both, this feature makes sure that one does crash the other when both are being played.