Each estimated time below is very minimal inside park time (inside park driving, short walk & photo) based on my personal experience.
On your way to Yellowstone via I-90, consider driving by Badland NP (2 hrs), visit Mt. Rushmore (2 hr) & Crazy Horse (2 hrs) at Black Hill (S. of Rapid City), further west, stop by Devil's Tower (2 hrs).
You may use 3 days rushing thru Yellowstone & Grand Teton.
Next you may want to stop by Bryce Caynon (4 hrs) & Zion NP (6 hrs) on your way down to LV from YS.
At Las Vegas (3 days, 2 nights), consider staying at Imperial Palace - not exotic outside appearance but decent interior, excellet location & affordable pricing.
On your way back from LV, you can stop by Hoover Dam (2 hrs), visit Grand Canyon (8 hrs), Monument Valley (3 hrs - driving inside the valley), Arches NP (4 hrs, 8 hrs if hiking to Delicate Arch) & Colorado NM (2 hrs).
It seem a very exhausting trip but also an exciting & unforgetable one. Enjoy & drive safely.
On your way to Yellowstone via I-90, consider driving by Badland NP (2 hrs), visit Mt. Rushmore (2 hr) & Crazy Horse (2 hrs) at Black Hill (S. of Rapid City), further west, stop by Devil's Tower (2 hrs).
You may use 3 days rushing thru Yellowstone & Grand Teton.
Next you may want to stop by Bryce Caynon (4 hrs) & Zion NP (6 hrs) on your way down to LV from YS.
At Las Vegas (3 days, 2 nights), consider staying at Imperial Palace - not exotic outside appearance but decent interior, excellet location & affordable pricing.
On your way back from LV, you can stop by Hoover Dam (2 hrs), visit Grand Canyon (8 hrs), Monument Valley (3 hrs - driving inside the valley), Arches NP (4 hrs, 8 hrs if hiking to Delicate Arch) & Colorado NM (2 hrs).
It seem a very exhausting trip but also an exciting & unforgetable one. Enjoy & drive safely.