The German, who lost the final in three sets to Jannik Sinner last year, ground past 41st-ranked Canadian Gabriel Diallo 6-7 (1/7), 6-1, 6-4, 6-2 on Rod Laver Arena.

It put him into round two at Melbourne Park for a 10th straight year as he looks to disrupt the domination of Sinner and world number one Carlos Alcaraz, who have shared the last eight major titles.

But he had to work hard to tame the lanky 24-year-old, who showed his potential with a maiden ATP title last year.

"He's a great player. Very young, very talented, very powerful," Zverev said.

"In the beginning, I was not playing good, I was giving him too many chances, I was too defensive.

"But happy with the way I played the second, third and fourth, because I thought that was quite a high level for me.

"It's a positive for sure," he added. "Because you have been tested and you know where you are and you know where your level is at, especially in difficult moments."

Zverev was broken early and slumped 4-1 behind in the opening set, struggling with the Canadian's booming serve.

Diallo went 40-0 up on his own serve with a chance to take a 5-2 lead, but the German dug deep to haul himself back to 4-4.

He saved a set point at 4-5 and it went to a tiebreak, where it was all Diallo.

Zverev regrouped at the changeover and came out firing, racing 4-0 clear with a double break to power through set two in 31 minutes and dial up the pressure.

He scored a crucial break in the seventh game of set three when Diallo fluffed a forehand from the baseline and took control as his opponent's error count surged.

Another break on Diallo's first service game in the fourth set put Zverev on his way to sealing the match.

His reward is a clash next with either Australian world number 49 Alexei Popyrin or 50th-ranked Frenchman Alexandre Muller.

Zverev finished the 2025 season with only one title, in Munich, having been beset by injuries.

It was enough to end as number three in the world behind Alcaraz and Sinner, but he disappointed at the other three Grand Slams with a major title still elusive.

Should he finally triumph in Melbourne on his 40th Slam appearance, the 28-year-old Zverev will go second on the Open era list for most attempts before winning a Grand Slam title.

Goran Ivanisevic holds the record, winning Wimbledon in 2001 on his 48th attempt.