The custodian could be excluded from the 23-man group due to travel to Poland and Ukraine for this summer's tournament
The 23-year-old's stellar performances for Hannover 96 had impressed national team coach Joachim Low sufficiently to be considered for a place in Germany's provisional 30-man shortlist.
Nevertheless, that could be as far as the former Manchester United youth player goes amidst competition from his fellow young keeper ter Stegen.
Low appeared to embolden speculation he would bring ter Stegen along as third choice goalkeeper in an interview granted to Sport Bild.
"Ter Stegen has great composure and a very good look. He has also played an outstanding season characterised by great performances."
The once-capped Zieler will have to wait till May 29 for Low's final squad to be announced.