Olympic champion Alexander Zverev has reached the second round of the Australian Open after a hard-fought 4-6, 6-3, 7-6 (7-3), 6-3 win over German countryman Dominik Koepfer on Tuesday. “In the beginning I wasn’t playing my best. I think I had a great tournament at the United Cup in Sydney, but then it is obviously very different coming here to Melbourne and playing at a Grand Slam,” Zverev said in his on-court interview after his three-hour, 12-minute win. “Especially in the first few rounds it is never easy, but you have to focus on yourself, focus on your own shots and focus on finding your…