Depends more on what sort of signal you expect to get out of the system. In general, I’d connect the Sonos Port to the Zone 2 outputs, with the understanding that many Amps don’t pass a digital connection, like the HDMI inputs to the second zone. That output would be line level, which is what the Sonos is looking for. Check your manual for the Denon to be sure, there are a few that can pass a digital output on to Zone 2, but they’re relatively few and far between.
Pretty much everything else on that device is either an input, or an amped speaker connection that wouldn’t be appropriate to push through a Sonos Port.
There’s no way, if you’re thinking of trying, to push a 5.1 signal through the Sonos Port, it’s only a stereo device.
You’d set up the Port as your line in connected to the Denon, and then could add the Sonos PLAY:1s as either single “rooms” or stereo “rooms” in the Sonos software to play the input on the Sonos Port.