Hi Mary, You'll have just over 400 miles to cover from Orange County to Zion National Park . It all depends on how many days you plan to be on the road. Here are a few suggestions:
Barstow - you can visit the Route 66 Mother Road Museum
Calico Ghost Town Campground - it was a silver mining town started in 1881 and is now the Official State Silver Rush Ghost Town. Don't miss the Mystery Shack.