I would think a route starting at Zion would go first to Bryce Canyon, then Capitol Reef, Arches/Moab, then Monument Valley and ending at the Grand Canyon. We have done the Grand Circle several times and have made the circle both directions. Certainly the amount of time you have for the total trip will dictate how much time you spend in any one location. The place we stayed the longest has always been in the Moab area. With Arches, Canyonlands, and Dead Horse SP you can spend a week without seeing everything there.