Hi Tom- Oh yes- I'm still using Zaino on the E500 and E320 Coupe but not so much anymore since there's now plenty of the product on. I'm using a rather vast supply of other products in the garage cabinet for the other vehicles.
You may be able to convince the shop to provide input to enhance the document (create ownerhip on their end) and then also execute it as a sign of good faith. This may be positioned from their perspective as appropriate in the best effort to provide the reassurance necessary to continue to do business with them (now and in the future).
hope this helps and let us know how things turn out.