Germany took a solid first step on Sunday in defence of their United Cup title with world number two Alexander Zverev and Laura Siegemund powering them past Brazil, who were knocked out of the mixed-team tournament.

Zverev assured the win by dominating Thiago Monteiro 6-4, 6-4 after Siegemund began with a 6-3, 1-6, 6-4 victory over Beatriz Haddad Maia, who is ranked 63 places above her at 17.

The result in Perth eliminated the South Americans from group play after a previous loss to China. Germany face the Chinese on Monday with the winner advancing to the quarter-finals.

In Sydney, women's world number four Jasmine Paolini crushed Belinda Bencic 6-1, 6-1 in just 57 minutes to ensure Italy beat Switzerland.

Men's world number six Casper Ruud, meanwhile, survived a tough examination from Tomas Machac, but his efforts were in vain as Norway crashed to the Czech Republic.

Zverev broke Monteiro in the opening game of each set, preventing him from threatening in the 80-minute contest.

The one-two singles punch left Germany in an unfamiliar position at the tournament it won last year.

"This is the first time we've ever been up 2-0," Zverev said. "Last year, I played deciding (mixed doubles) matches every time.

"It's nice to have this (tie) in the bag. I'm very happy to be playing for Germany again."

Siegemund fought for more than two-and-a-half hours to subdue Haddad Maia, winning five first-set games in a row before stumbling to lose the second set.

The German came out ahead after three consecutive service breaks late in the final set for a 5-4 lead and secured her win on a first match point.

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

- Tough start for Ruud-

Paolini had a sensational 2024, finishing runner-up at Roland Garros and Wimbledon, and she carried that form into her first match of the new season.

Bencic, herself a one-time world number four, is on the comeback after having a baby and was completely outclassed.

"I played a really good match. Today everything worked really well," said Paolini.

"I was serving and returning well, and I think that was the key."

Her teammate Flavio Cobolli had earlier defeated Dominic Stricker 6-3, 7-6 (6/2) to give Italy a 1-0 lead.

Ruud, the highest-ranked Norwegian in history, was put through his paces over nearly three hours before downing Machac 7-6 (7/6), 5-7, 6-4.

His win levelled the tie 1-1 after Karolina Muchova got the Czechs off to a flying start with a 6-2, 6-2 romp over Malene Helgo.

Machac and Muchova teamed up in the deciding mixed doubles to beat Viktor Durasovic and Ulrikke Eikeri 6-4, 6-4 with Ruud opting out after needing treatment on his left quad during the singles.

"You kind of hope that it won't be that tough, but what a way to start the new season," said Ruud, who banked 2024 tournament wins at Geneva and Barcelona.

"If every match is going to be this tough, it's going to be a tough (season)."

Ruud broke 25th-ranked Machac early in the third set to assume control, but he will be concerned at facing nine break points through the match.

The Coco Gauff-led United States -- the 2023 winners -- take on Canada late in the final group match in Perth.

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