Zverev arrived in Melbourne lacking confidence after losing all three of his singles matches at the inaugural ATP Cup to Australia’s Alex de Minaur, Greek Stefanos Tsitsipas and Canada’s Denis Shapovalov.
Seventh seed Alexander Zverev credited a stress-free life off court for his strong run at the Australian Open after marching into the fourth round with a 6-2 6-2 6-4 win over Spanish veteran Fernando Verdasco on Saturday.
Zverev arrived in Melbourne lacking confidence after losing all three of his singles matches at the inaugural ATP Cup to Australia's Alex de Minaur, Greek Stefanos Tsitsipas and Canada's Denis Shapovalov.
His serve has always been one of his biggest weapons but it looked in complete disarray as the German totalled 31 double-faults during the three defeats.
But the 22-year-old has bounced back splendidly at the year's first Grand Slam, where he has not lost a set as he advanced to the fourth round for the second straight time.
"Generally I'm happy outside the court, happy on the court, happy in life," he said. "Then I think you play your best.
"When you have stress outside, when you have stress that I had last year with all sorts of things, you're not going to perform your best. I have a pretty calm life right now, which is nice for me."
Zverev was once considered one of the leading 'Next Gen' contenders to break the Grand Slam hegemony of Novak Djokovic, Rafa Nadal and Roger Federer who have shared the last 12 majors between them.
But the German, who beat Federer and Djokovic on his way to the 2018 ATP Finals title, fell off the radar as he failed to get past the quarter-finals at the majors.
"It's so far been a good week for me... It has been getting better. Today was the best match I think I've played so far," Zverev said.
He did have three double faults against Verdasco at the Margaret Court Arena but also served 15 aces while hitting 34 winners in the match.
Zverev broke the 36-year-old Verdasco, a former top-10 player who is currently ranked 51, twice in each of the first two sets.
Verdasco refused to give up and broke his opponent in the third to go up 4-2 but Zverev got the set back on serve in the next game and then broke the Spaniard again in the ninth game before serving out to complete his victory.
Zverev will meet Russian Andrey Rublev, who extended his winning streak to 11-0 for the season with a 2-6 7-6(3) 6-4 7-6(4) win over 11th seed David Goffin earlier on Saturday, for a place in the quarter-finals.
Zverev said he had been friends with Rublev since they were 10-year-olds.
"He's one of the most hard-hitting players on tour. Out of every position, he can hit a winner," he said. "He's somebody that is very young still but always is working and always is improving."