To do before:
We suggest to cable via ethernet the Master group device to the router (if it’s not possible use the 5GHz network as preference)
To do next:
Click on the MULTIROOM icon on the top right corner of the User Interface
Click on GROUP DEVICES
Click on ADD to add the selected device to the group
Note: no Master group volume control available ; it's not possible to create group between devices on different networks
Your music is not perfectly synchronized?
Go to SOURCES→MULTIROOM→SETTINGS
increase the hardware latency in msec unit, of the relate device
adjust the buffer size in msec unit (in case your hardware/network connection is not performant). This will delay all the network devices