US Open: Zverev and Kerber through on good day for Germans

For someone so obviously talented, Alexander Zverev's record of being knocked out in the second round of his last three appearances at Flushing Meadows is a dismal record.

But the 21-year-old looks in majestic form so far this year, with a 6-4, 6-4, 6-2 win over France's Nicholas Mahut meaning he's dropped only 15 games in his two matches to date.

The number four seed was on top of his veteran opponent throughout, hitting 43 winners and 10 aces while converting each of his five break points. Incredibly, his first serve average was 134 miles per hour.

Zverev's reward for the win is a last 16 match against compatriot Philipp Kohlschreiber, who came back from a first set loss to beat Australia's Matt Ebden 6-7, 6-3, 6-2, 6-0.

Kerber marches on

Much like Zverev, Kerber looked totally in control early in her match against Sweden's Johanna Larsson, racing in to a 4-1 lead in the second set after winning the first 6-2.

But, as she sometimes has a tendency to do, the German player let things slip, allowing her opponent to hold off two match points at 5-3 before the Swede won four straight games to steal the second set 7-5.

But the Wimbledon champion, who won this tournament in a golden 2016, finally stopped Larsson's momentum in the third set, breaking her to go up 5-4, then served out the gruelling match to win 6-2, 5-7, 6-4 in more than two hours.

"I think we both really played on a really high level from the first point," Kerber said. "In the end it was one or two points to decide the match."

With temperatures flirting with 37 degrees Celsius on Thursday, tournament officials again implemented an extreme heat policy, which both players took advantage of after the second set. 

Kerber will play Slovakia's Dominika Cibulková, seeded 29, in round 3.