If you have several AirPlay 2 speakers at home, you can connect them for multi-room output. With the HomePods you can do this by voice, alternatively, it can of course also be done directly via Mac, iPhone and iPad. We have published instructions on the subject before:
Now, I’m quite happy to use shortcuts to stream music to my speakers, but there’s always been something that has bothered me in the past. iOS 15 .3 can transfer music to a HomePod via shortcut or use AirPlay for transfer, but multiple destinations are not addressable. But that will change in the shortcuts with the upcoming iOS 15 .4. You can now activate multiple targets there.
It is important if you want to try the whole thing: You have to change the currently English “Set” in the selection to “Add” and select the desired speakers. With Set, you would only select one speaker, with “Add” you add it to a group. If you then play music, you can run the shortcut either via Siri on your iPhone or manually.