Do you have access to your airline's zed agreements? We have a list, by carrier, of the terms between the two airlines. None of our zeds are ticket-able in any class but coach for nonrev. I would recommend you ask prior to trying to get a zed "ticket" at your SW counter and what the terms are for each carrier. Zeds are only interchangable with carriers that have an agreemetn w/SW. You may have Finnair; we don't--we may have EVA, maybe SW doesn't...