The American was forced to battle not only Zverev but also challenging weather conditions during a dramatic encounter at the ATP-WTA Cincinnati Masters.
The match was interrupted for around 90 minutes by rain during the seventh game of the second set. There were also two additional five-minute pauses as officials worked to dry the court.
Despite the disruptions, Paul kept his composure and eventually turned the contest in his favour.
Zverev, the reigning French Open champion, had a huge opportunity to close out the match in the second-set tiebreak. The German led 6-5 and was just one point away from victory, but he missed a volley into the net.
Paul seized the opportunity, forced the match into a deciding set and completed the comeback.
Paul seals another win over Zverev
Zverev appeared to have regained control in the final set when he broke Paul to take a 4-2 lead. However, Paul immediately responded by breaking back in the following game.
The American then broke again to move 5-4 ahead before confidently serving out the match.
The victory marked Paul’s third win over Zverev in their last four meetings, underlining his growing confidence against the German.
“I’m not sure how I did it,” Paul said after the match.
He credited his aggressive returning and Zverev’s mistakes for helping him stay alive.
Paul also said he was enjoying his tennis and hoped to build momentum ahead of the US Open, which begins on August 30.
Paul to face Cobolli in quarter-finals
Paul will next meet Italy’s Flavio Cobolli, who also survived a gruelling three-set battle.
Cobolli defeated Spanish teenager Rafael Jodar 4-6, 7-6 (7/3), 6-3 after two and a half hours.
The Italian has now won all three of his matches in Cincinnati in three sets and reached his second Masters-level quarter-final of the season, following his run in Madrid.
Cobolli also ended Jodar’s impressive run of reaching the quarter-finals in seven of his previous eight tournaments.
Swiatek continues strong Cincinnati run
In the women’s draw, defending champion Iga Swiatek advanced to the quarter-finals after defeating France’s Diane Parry 6-3, 6-3.
The seventh-seeded Swiatek needed four match points to close out the contest but secured the victory in 88 minutes.
The six-time Grand Slam champion has now reached the Cincinnati quarter-finals for the fourth consecutive time and her 30th quarter-final at WTA 1000 level.
Swiatek will face Elena Rybakina in a rematch of last week’s Toronto final. Rybakina defeated Diana Shnaider 6-4, 6-4.
Meanwhile, several Grand Slam champions were eliminated. French Open winner Mirra Andreeva lost to Ukraine’s Marta Kostyuk, while Wimbledon champion Linda Noskova was beaten by Amanda Anisimova.
Anisimova will next face third seed Jessica Pegula, who edged past Sorana Cirstea 6-2, 4-6, 7-5.
