6 days from Glacier to Moab would be rather slow unless you have some way points you want to visit on the way. And on I-15 you will avoid most of the mountains. When is the BIG point, as pointed out Moab/Arches is hotter than Hades from June thru September and so is Zion. Glacier is frequently snowed in thru mid July.
I'd go to Moab area first then Yellowstone/Tetons spending much more than a few days and then Glacier. That make more sense from the weather standpoint.
If you plan to spend time camping in any of those parks you better have reservations already made. Even private parks outside need reservations.