If you were referring to me Drew, I haven't done the zip line is down there. We climb or hike when down there. Assume they are reffering to this one
RedZipLine
The Red's a great place for scenic, curvy roads. Lots to see and do there too. The hike up to Natural Bridge is great (there's a lift up to it also). There's a Via Ferrata that's really awesome if folks wanted to get dirty and climb on the cliffs. Kinda have to be in shape for that one.
Really cool one-lane tunnel in Nada that some of us might collapse if we rev our engines. Some really great pizza at Miguels. State lodge, state camp ground, and other more rustic camp grounds.