Hi. You can't power six speakers in Zone 2 independenty from that Marantz, as it only has two speaker terminals that can be assigned to that zone. However, because you have a 2.1 setup in your main area, I checked into if you could run your "main zone" setup as Zone 2, and then power the ceiling speakers from the main zone speaker connections...but you can't do that with the components that you want to use. Even if you use the speaker-level outputs for Zone 2, you can't play anything from the digital inputs (e.g. HDMI) through Zone 2.
So, as far as I can tell, you'd need to do two things if you want to use the Zone 2 capability of the Marantz with your ceiling speakers: (1) connect the CD player using analog connections, and (2) amplify at least four of the ceiling speakers with another source (which could be your older Pioneer or Yamaha receivers being used just for their amps).
EDIT: I was responding at the same time as Craig. He's right that you can use a speaker selector.