OK, my thoughts: I would draw a big X through Lake Powell. It's really not that interesting or pleasant. It's going to be MUCH too hot to enjoy the lake, which by the way is heavily polluted, especially with recent low water levels. And it is often very windy at Wahweap. 109 degrees and blowing dust doth not a pleasant experience make.
I assume you have campsite reservations for Zion. You'll need them. Very very hot in summer, which will make Bryce a welcome destination. Great place to be when the rest of southern Utah is cooking.
You included Mesa Verde in with Arches and Canyonlands, but it's several hours away. If you are then going to Glenwood Springs, that's a double back to I-70 of almost 400 miles round trip. Mesa Verde is interesting, but I don't think it's worth that degree of detour. Hwy 550 north to Montrose from Durango is a fantastic drive (and probably worth making that detour if you're in a car), but not so great for RVs. If you want to see Anasazi ruins, there are plenty of lesser known but just as interesting sites in southern Utah.
As you're coming from the west, going to Estes Park and then into Rocky Mountain NP is a bit of a double-back. Suggest you enter the park from the west via Grand Lake. Beautiful drive!
Definitely recommend you stay in the mountains to go down to Colo Springs. Any one of a number of north-south routes takes you through some fantastic country.
Colorado Springs to Mammoth sounds like quite a stretch for only two days, but you can shave off a day in Mammoth if necessary. You really only need one full day to see the cave, and there's not much else to see in the area. Louisville is...Louisville.