In the final, he'll play rising Italian star Flavio Cobolli, who advanced to the championship match later on Friday when his compatriot, world no.104 Matteo Arnaldi, had to withdraw due to a virus.
Zverev has been an overwhelming favourite for the title ever since world No.1 Jannik Sinner struggled in the first week's heat wave in Paris, bowing out after wasting a two-set and 5-1 lead against Juan Manuel Cerundolo in the second round.
The 29-year-old German, who 's lost three major finals, including one at Roland Garros two years ago, is trying to shake off the tag of best men's player never to win a slam and he'll face 10th seed Cobolli, given a free pass to the showdown because of the problems for luckless Arnaldi.
Arnaldi had spent a monumental 19 hours 42 minutes on court to reach the semi-final — more than anyone at a grand slam since 1991.
He reported that he'd been vomiting overnight. "I tried to get ready ... but every time I get up I feel dizzy," Arnaldi said. "I can't move and I can't eat and I can't drink. So there was really no way that I will be able to play."
The 24-year-old Cobolli reckoned that his friend's withdrawal had also left him emotional.
"It was tough for me," he shrugged. "When he came to me with the news an hour ago, I almost cried. I have a lot of respect for him and he's an inspiration for a lot of us."
World no.3 Zverev will go into his fourth final against world No.14 Coboilli as odds-on favourite after he subdued the challenge of 20-year-old Czech Mensik, who'd knocked out Australian No.1 Alex de Minaur in the third round.
A tight opening set on a sun-kissed Court Philippe Chatrier on Friday tilted Zverev's way when he struck a backhand crosscourt winner in the 11th game to bring up a break point, and he nudged ahead crucially with a delicate shot that Mensik sent into the net.
The world No.3 then grabbed another early break at the start of the second set, looking increasingly dominant before Mensik needed a long medical timeout for a neck issue.
Two sets down, he seemed refreshed, mixing his booming serve with deft drop shots to break for a 4-2 lead en route to winning the third set. Zverev, though, powered through the fourth with no drama to prevail.
Sunday will be Zverev's best chance yet of glory after he lost to reigning champ Carlos Alcaraz from two-sets-to-one up two years ago.
He came even closer in his maiden final against Dominic Thiem at the US Open in 2020, blowing a two-set lead and losing in a deciding tie-break, while he was well beaten by Sinner in the Australian Open final last year.
"I knew that it would be my toughest challenge. I managed it and I won, so I'm happy," said Zverev, who became only the fifth active player to reach multiple Roland Garros finals.
