After Jan-Lennard Struff survived a 34-ace onslaught from John Isner to prevail 7-6(7), 4-6, 7-5, Zverev broke Fritz early in both sets before capitalising on a sixth match point en route to victory in the Group C tie.
The win moved Germany, who lost to Britain in their opener, to 1-1 in the group before they face Canada on Thursday.
USA picks up a point ✅Fritz/Isner fly by Krawietz/Puetz 6-0, 6-3 in under an hour#ATPCup https://t.co/9UCisLcA1T
— ATPCup (@ATPCup) 1641273776000
“Until the last game it was a good level for my second match of year. It was very intense and hard hitting,” said Zverev, who will be gunning for glory at the Australian Open this month.
“The most important thing is that team Germany won and we gave ourselves the best chance to qualify for the semi-finals.”
World number seven Berrettini saw off Ugo Humbert 6-4, 7-6(6) in Group B after Jannik Sinner had defeated Arthur Rinderknech 6-3, 7-6(3).
Humbert had stunned Russian world number two Daniil Medvedev on Sunday and threatened another upset after forcing a tiebreak in the second set, but Berrettini dominated with his serve to clinch the tie for Italy.
Hands up if you want more Sinnettini 🙋♂️#ATPCup | #TeamItaly https://t.co/y9ZIki4KpV
— ATPCup (@ATPCup) 1641273475000
“(It was) a really tough match, especially in these conditions. He’s a great server, a tricky player,” said Berrettini, who lost his opening singles match to Australian Alex de Minaur.
“I had to play my best tennis in the important moments to win the match… I’m really happy (with) my performance.”
U.S. Open champion Medvedev will take on De Minaur later on Tuesday as Russia continue the defence of their ATP Cup title against Australia.
Canadian Denis Shapovalov will face Britain’s Dan Evans while Felix Auger-Aliassime takes on Cameron Norrie in Group C in the other evening ties on Ken Rosewall Arena.