<p>Welcomed by a supportive crowd, top seed Zverev beat Yannick Hanfmann 6-3, 7-6(4) in an all-German duel to keep his hopes alive of a first grass court title in his career.</p><p>Zverev broke Hanfmann once to take the opening set. In the second, both players held firm on their own serve to force a tie break, which Zverev won comfortably.</p><p>The top seed said he was still adjusting from clay, his preferred surface, to grass, saying he wanted to improve his return, which "is the most important shot on grass".</p><p>"<strong>I've only been on a grass court for a couple of days but I'm through to the quarter-finals, so I'm happy with that</strong>," Zverev added.</p><p>The 29-year-old beat Italy's Flavio Cobolli in a seesawing five-set Roland Garros showpiece to break through for a first-ever Grand Slam title.</p><p>The former Olympic gold medallist had come agonisingly close but had never broken through, losing three Grand Slam finals.</p><p>On Wednesday, Cobolli got a modicum of revenge for the Roland Garros defeat by eliminating Zverev in the doubles on the Halle grass.</p><p>Zverev, who made the final at the Wimbledon warm-up tournament in 2016 and 2017, will face either Raphael Collignon or Mattia Bellucci on Friday for a place in the semi-finals.</p><p>Earlier on Thursday, world number five Ben Shelton beat fellow American Ethan Quinn 6-4, 5-7, 6-4 to set up a quarter-final meeting with Taylor Fritz, who he beat in the final of Sunday's ATP event in Stuttgart.</p><p>In the other quarter-finals, Canadian world number four Felix Auger Aliassime will face American Frances Tiafoe while 2021 US Open champion Daniil Medvedev takes on German Daniel Altmaier.</p>