Zverev through in Munich

Zverev fired 11 aces in beating his fellow German 4-6 6-1 6-2.

Victor Estrella Burgos is also through to the second round after a 7-6 (7/4) 6-4 win over Viktor Troicki.

Organisers also confirmed that Gael Monfils, the second seed here, has withdrawn due to a knee injury, replaced by Austrian Jurgen Melzer.