Since leaving United, Zieler has won a call-up to the senior Germany squad.
He told manutd.com: "I played most of the time for the Reserves but it's still been a good time for me and I think I learned a lot. I got a lot of experience and many memories as I was there for five years. I think I developed as a player. United gave me a chance and it was a really helpful time for me as a person and a footballer."