Rented bicycles at Zion, the shuttle will take you and your bike to the end of the park. We hiked and biked our way back across the day. (Am I the baddie?)
I almost did exactly this, and next time I’m there, I probably will!
No way I’m riding those shuttles again. Nothing quite shatters the peace and awe that comes with the scenery like a kid screaming and kicking non stop while his parents act helpless.