Team Europe, captained by Yannick Noah, entered the third and final day needing two victories to reclaim the trophy.
Sunday's matches were worth three points each, with the first team to reach 13 points claiming the Laver Cup. Match wins were worth one point on Friday and two points on Saturday.
French Open runner-up Flavio Cobolli of Italy teamed up with Czech Jakub Mensik to open the final day's action, moving Team Europe to within one win of the title after a 7-5, 6-3 victory over Team World's Taylor Fritz and Alex de Minaur that extended their lead to 10-5.
French Open and US Open champion Zverev then took centre stage against Tien, with the German prevailing 7-6(3), 6-3 to seal the title for Europe.
The victory marked the fourth time Zverev had helped to clinch the Laver Cup for Team Europe. He also secured the winning points in Chicago in 2018, Geneva in 2019, and in Boston in 2021 when he won the doubles alongside Russian Andrey Rublev.
Zverev's victory sparked jubilant celebrations, with the European players leaping in celebration and singing on court.
'Great chemistry and team effort'
"I'm happy that I did it today," Zverev said. "But massive credit to the entire Team World. They pushed us all the way.
"I think we had a great team, great team chemistry and a great team effort. We're definitely happy that we won!"
Seven-time Grand Slam champion Carlos Alcaraz, who returned at Flushing Meadows after a lengthy layoff due to a wrist injury and has looked sharp since, had been scheduled to face Australian De Minaur in a later singles match.
Rising 20-year-old Spaniard Rafael Jodar was due to play Fritz, but neither match was needed after Zverev wrapped up the contest.
"We had three chances to close it out in the singles," Zverev added.
"Especially with Carlos playing after me, I think that gives me a lot of confidence and gives me a little bit of freedom to play.
"But still, it was an incredibly tough match. Credit to Learner as well.
"I think Carlos is also very happy that I closed it out. And me too, by the way! I'm very happy that I won."
Hollywood star Leonardo DiCaprio and Swiss tennis great Roger Federer, a co-founder and co-owner of the Laver Cup, were among the spectators at a packed O2 Arena.
Team World is made up of players from continents outside Europe. The annual tournament, which began in 2017, is intended to be tennis' equivalent of golf's Ryder Cup.
Team Europe lifted the trophy in 2017, 2018, 2019, 2021 and 2024 before adding this year's crown, while Team World won the title in 2022, 2023 and 2025.
The 2027 edition, which will mark the tournament's 10th staging, will be held at the Intuit Dome in Inglewood, California.