if using shairtunes as plugin for the squeezebox server, you can currently not send the output to synchronized squeezeplayers.
But if your focus is using airplay, you may use shairport (standalone player on tab “Audioplayer” in Web interface of Max2Play). Depending on which device (Raspberry PI / ODROID) and soundcard (e.g. HiFiBerry) you use, this shairport player may run at the same time as squeezelite does. With this setup (shairport activated on all devices running Max2Play) you can select multiple airplay devices from your idevice and let them play together (synchronize the players with your idevice like itunes on Mac).
Following setups work with Squeezelite and Shairport running at the same time:
– Raspberry PI without external soundcard (using HDMI or headphone jack)
– ODROID U3/XU3/XU4/C1
– Most USB-DACs that are connected to the ODROID / Raspberry PI
Not working in this modus are soundcards like HiFiBerry and others connected to the GPIO Pins on the Rasbperry.