I have done a simple zigbee and ir system without internet, but with a router in place. I set the controller to a static ip, and it has been working fine for years. It was in a boardroom and the IT guys did not want it on there commercial network.
I have a simpler solution, use the zone2 on the marantz for the laundry zone. If you need audio from the matrix just feed audio to marantz, do not hook up out from the matrix and in to both pieces.