Olympic champion Alexander Zverev has survived a five-set thirller against Slovakian qualifier Lukas Klein to claim his 400th tour-level win and advance to the third round of the Australian Open on Thursday. The German needed four and a half hours to complete a hard-fought 7-5, 3-6, 4-6, 7-6 (7-5), 7-6 (10-7) win. “He played incredible. He was hitting every single ball as hard as he could from both sides. I didn’t really know what to do a lot of the times. To be honest, he probably deserved to win the match more than me today. But that’s how tennis goes sometimes,” Zverev said. Zverev, who hel…