There are 2 ways depending on your RV size:
1) Hwy 9 through Hurricane and through Zion Nat'l Park. There will be tunnels. Many RVers drive this route if they're not oversized. Check the Zion official web site for all the specifics. Then Hwy 89 south to Kanab.
2) Hwy 9 to Hurricane and Hwy UT59 which becomes AZ389 to Fredonia and north on Hwy 89 to Kanab. This is an easy drive - no tunnels.
Have a good trip!
Full-timed for 16 Years . . .
Traveled 8 yr in a 2004 Newmar Dutch Star 40' Diesel
& 8 yr in a 33' Travel Supreme 5th wheel