I currently do this throughout my house across 4 different systems. One is my main home theater system, the other a vintage console stereo, the next a Fisher 400, and finally a set of computer speakers. I do it 2 different ways. The first is I have Google Chromecast Audio devices on each of them. They are no longer made, but, you can get them on eBay. They work great and use analog 3.5mm stereo jacks that you just put a 3.5-RCA splitter on. They’re wireless so zero cabling. To sync them up you simple create a “group” that includes all the devices you want synced up and name that group. Mine is called “the house”. The you choose whichever music streaming service you want as your default and simple say, “Hey Google, play Miles Davis in The House”. Then it streams in sync to each system wirelessly. In a separate input I do the exact same thing with Apple Airport Express’. They are also no longer made, but, again eBay. I do the same thing with those for my downloaded music on my computer. I just select all the devices from my MacBook in the audio drop down menu when Apple Music app is launched. Hope that helps a little.