The seventh seed has regained his touch, powering through to his first grand slam quarter-final on a hard court without losing a set.

It will be Zverev's third appearance in the last eight at a major after reaching the quarter-finals at the past two French Opens.

The 22-year-old's chances of a deep run at Melbourne Park looked shot after a disastrous ATP Cup where he failed to win a match.

His serve was out, and even Zverev himself conceded he hadn't played much worse during his career.

But he has a serious opportunity to shed his grand-slam underachiever tag when he takes on three-time major winner Stan Wawrinka on Wednesday.

Zverev said he was playing better with each match following his clinical fourth-round victory over Russian Andrey Rublev 6-4 6-4 6-4 in just 96 minutes.

"I don't have a reason not to be (confident) right now. I've played against very good opponents so far this week," he told reporters.

"The first match wasn't the best, but I won. The second match wasn't the best either, but I won. I hope it will continue being like that.

"There's only the eight best players in the world left. I think everybody who's still here has a chance."

The German is well aware Wawrinka presents his biggest challenge yet, despite winning his two career meetings against the 2014 Australian Open Champion.

The 15th seed Swiss veteran outlasted Russian rising star Daniil Medvedev in a five-set fourth-round thriller, battling through his ongoing knee problems.

"He's still one of the toughest players to play, especially here in Australia," Zverev said.

Wawrinka, who had lost his previous two meetings against Medvedev, said it was the best he had played since his 2017 knee surgery.

"Physically I'm moving better than last year. So I'm improving," Wawrinka said.

"The week before (coming) here, I was really feeling at the top level."

The winner of this match will face world No.1 Rafael Nadal or Austrian fifth seed Dominic Thiem in a semi-final showdown.

Australian Associated Press