World No. 2 Alexander Zverev started his Australian Open preparation with a clinical victory on Sunday as defending champion Germany swept past Brazil in the United Cup.

Top-seeded United States, the Czech Republic and Italy were the other winners on Day 3 of the mixed team tennis tournament.

Taylor Fritz of the United States hits a return during the men's singles match against Felix Auger-Aliassime of Canada in the Group A round robin match between the United States and Canada at the 2025 United Cup tennis tournament in Perth, Australia, Dec. 29, 2024. (Photo by Zhou Dan/Xinhua)

Zverev was in full control at Perth's RAC Arena and overwhelmed No. 109 Thiago Monteiro 6-4, 6-4 in one hour and 17 minutes. He was dominant on serve with 11 aces as the 27-year-old made a successful start to the Australian season which he hopes will culminate in a drought-breaking Grand Slam title.

Zverev was runner-up at the 2020 US Open and 2024 French Open, and is a two-time semifinalist at Melbourne Park.

"I'm very happy to be back playing for Germany again. I'm enjoying my time on the court," he said.

Zverev wrapped up Germany's victory in the tournament opener after Laura Siegemund upset world No. 17 Beatriz Haddad Maia 6-3, 1-6, 6-4 in two hours and 33 minutes.

"It's good to pull your best game out of the pocket in the first match of the season," the 80th-ranked Siegemund said. "I tried to stay cool and take my advantages."

The 3-0 result in Group E knocks winless Brazil out of the tournament. China and Germany will clash on Monday with the winner to qualify for the quarterfinals.

The United States edged Canada 2-1 at RAC Arena with Coco Gauff and Taylor Fritz defeating Leylah Fernandez and Felix Auger-Aliassime 7-6 (2), 7-5 in a mixed doubles match that finished at 1 a.m. on Monday morning.

World No. 3 Gauff had given the U.S. a flying start after barely raising a sweat against former US Open finalist Fernandez to win 6-3, 6-2 in the first matchup of the young stars.

Gauff left off from her season-ending triumph at the WTA Finals with an impressive performance marked by powerful groundstrokes and speed around the court.

"Very happy," said 2023 US Open champion Gauff. "I knew going in it was going to be a tough match but I'm super happy with how I played and happy to get a point on the board for my team."

But the fourth-ranked Fritz had a stumble after losing to Auger-Aliassime, who produced a remarkable 4-6, 7-5, 6-3 comeback victory.

Playing with trademark ferocity, Fritz was in total control until he failed to serve the match out in the 10th game of the second set.

Auger-Aliassime took advantage to stage a stirring fightback in a disappointing result for Fritz, who fell short to world No. 1 Jannik Sinner at the US Open in his first Grand Slam final.

In Sydney, world No. 6 Casper Ruud survived a major challenge from the Czech Republic's Tomas Machac to prevail 7-6 (6), 5-7, 6-4 in a brutal contest lasting almost three hours.

Ruud received treatment on his legs on two consecutive changeovers in the third set, but had enough in the tank to thwart Machac's stern challenge.

He kept Norway alive in the Group B tie after 2023 French Open finalist Karolina Muchova swept past Malene Helgo 6-2, 6-2.

"You kind of hope that it won't be that tough, but what a way to start the new season," said Ruud, who is a three-time Grand Slam finalist. "I was a little bit tired towards the end. It hasn't been the longest of off-seasons."

A fatigued Ruud understandably did not back up for the mixed doubles, and the Czech Republic capitalized with Muchova and Machac comfortably defeating Norwegian pairing Viktor Durasovic and Ulrikke Eikeri.

In the later tie in Sydney, Jasmine Paolini and Flavio Cobolli prevailed in their singles matches as Italy won 3-0 over Switzerland, who missed the chance of sealing a quarterfinal spot.

Cobolli gave Italy a perfect start with a 6-3, 7-6 (2) victory over Dominic Stricker before Paolini, a finalist at the 2024 French Open and Wimbledon, crushed Belinda Bencic 6-1, 6-1 in less than an hour.

Fourth-ranked Paolini was ruthless to halt the comeback of Bencic, who has recently returned from maternity leave. "Today everything worked really well," said 28-year-old Paolini. "I was serving well, I was returning very well. I think that was the key."

Women's world No. 2 Iga Swiatek starts her season as Poland takes on Norway in the main attraction on Monday.