Return To Zed is the fourth of four story missions that must be performed in order for the Catch-A-Ride system to work.
"Head on back to Zed. Let him know you fixed the Catch-A-Ride and opened up the main road. He'll be happy to hear it. Squeeze him a little and I'm sure he'll cough up a little somethin' for your trouble. If he don't, tell him Scooter's gonna come out there and kick his quack ass."
Travel back to Fyrestone and talk to Dr. Zed to complete the mission.
"Some of the locals heard you opened that barricade and hightailed it for New Haven. I wish them the best of luck, but the area is still crawlin' with bandits. Sledge is still out there, and just between you and me, I ain't goin' nowhere until I know for sure I won't end up danglin' from a pike."