Depending on from where you are coming you may also want to consider renting in Vegas and taking in Hoover Dam as well and then heading up to Zion. Another option may be in St. Georges, Utah as another spot to rent a car.
We did the "Great Circle" route a few years ago and it was one of the most spectacular trips we have ever taken. Our routing took us from Vegas to Zion, Bryce, Capitol Reef, Canyonlands, Kodachrome Basin, Arches, Mesa Verde, and Grand Canyon. If you do get up to Capitol Reef make sure you stop at Cafe Diablo.
2011 Berkshire 390bh