There are at least two pay shower facilities at ZRH once outside customs. One is at the Radisson BLU hotel that is inside the airport building (closer to the Terminal A side), and another one is near the Information/Help counter in the adjacent building (where the shops and train station are). For the latter, once you exit customs, take the escalator up to the next level, use the “bridge” to cross over to the next building and look for the Information counter to the left; they should have two shower rooms available for rental.