You don't want to output from one matrix into another. However if you're really just talking about music, you can run audio from say a CORE 5 controller, which has 3 analog outs and 3 digital outs, and run 3 to each matrix (or 4 to the AMS16 and 2 to the AMS8 is probably how I would do it actually), and you'd be fine, and would have the ability to have all zones play in sync if you wanted to still.