https://www.monoprice.com/product?p_id=10761
I use this. Some kid wrote a python program that controls it over an rs232 dongle connected to a pi/PC. I containerized it and have it running alongside my other home automation containers. It's a little pricey but gives fantastic sound. I have 2 Chromecast audios as my inputs (I know, I know). So any input of the 6 can be directed to any of the six zones. You can also run all 6 zones off of the same input if you choose. The local control stations connect over cat5e but aren't networked. I've been very happy with it.