I would talk to your own pass travel department to be sure of the exact procedures, but I know that usually you need to purchase the ZED at your own airline's ticket counter. At SkyWest, we piggyback on Delta's interline agreements and have to make a listing online ahead of time, then purchase the ticket itself (it's a paper ticket on most airlines, so hang on to it!) at a Delta ticket counter (which kind of sucks, since I work at a United Express-only station and have to drive about 100 miles to get to a Delta one).