Depending on the size of the Palazzo, the difference between GVWR and GCWR is 4000 or 5000 pounds. I'd guess, and it's a guess, the Suburban is at least 5000 and closer to 6000. Coach has the Cummins 300HP ISB diesel, would probably would pull OK, and chances are the coach won't be loaded to the full 26000 or 28000 GVWR.
I see lots of people with diesel pushers towing big vehicles. Hummers, Suburbans, Silverados, etc etc. I just pray they have supplemental braking with a breakaway feature. That's a huge deadly missile if it gets loose, and the coach that lost it won't be the vehicle it collides with.