Hello Coothesseam37
From my experience, this service is (no longer) offered to customers with starting point outside of Switzerland. The green customs declaration is nowadays solely available in Switzerland, thus the service can be offered to people from Switzerland on their return flight only.
However, as I have worked many years at ZRH, I can tell you that there is no big deal in picking up the luggage yourself at the baggage hall, and to pass customs. After customs, you can drop it at the SBB Travel Center for delivery to your end destination (note the delivery times)
It is also possible to take your luggage with you on the train. Almost all trains have floor level entry which make travel with luggage easy.
Kind regards,
Roland