If you have a blown zone, I would take an hour to take it apart and see if the fuse replacement is easy or not. Sonance stuff doesn't fail often. Also worth calling to see if it is still under warranty. They fix things. But, you should then only use one channel of the Xantech amp, and I would use it for a single pair of speakers.
The Marantz is completely pointless unless you intend to use it as your actual source for audio. If it is the source for audio, then fine, if you intend to use something like a Sonos or some other similar streaming device, then just hook that device directly to the amplifiers. If you intend to hook a source into the Marantz, then turn the Marantz on/off, then use a different control for that source, then the Marantz is simply adding a completely pointless extra step to the entire system and complicating things.
SOURCE --> SONANCE BUS INPUT L/R
SONANCE BUS OUTPUT BUFFERED L/R --> XANTECH BUS INPUT L/R