You folks inspired me so I built the device that I speculated about earlier in this thread.
If you’re interested, here’s what I did.
I’m curious what @Michael_Harris will come up with - if he figures out a comparable or better solution built around a Raspberry Pi, that could easily be swapped in. The Apple remote is a nice part of this. I didn’t realize earlier that controlling zone volume is done with up down presses on the control wheel. It all works really well.