Now the pair of 20-somethings will meet each other for a berth in the French Open final after straight-set quarterfinal victories Tuesday.
The No. 5-seeded Tsitsipas reached his fourth major semifinal -- and second in a row at Roland Garros -- by upending No. 2 Daniil Medvedev 6-3, 7-6 (3), 7-5 at Court Philippe Chatrier in the last no-spectator night session of this year's tournament.
"I feel privileged that I'm in that position, and I feel obviously I've put in a lot of daily hard work (that) has been a key element of me being here,'' Tsitsipas said. "But, you know, my ego tells me I want more.''
Tsitsipas escaped two set points held by two-time Slam runner-up Medvedev at 5-4 in the second, but otherwise required only slightly more work than was demanded of Zverev in his 6-4, 6-1, 6-1 victory over unseeded Alejandro Davidovich Fokina.
That put No. 6 Zverev in his third Slam semifinal, first in Paris.
Tsitsipas is a 22-year-old from Greece. Zverev is a 24-year-old from Germany. Both have won Masters 1000 titles on red clay this year. Both have won the season-ending ATP Finals. Both intend to -- and, truthfully, are expected to -- claim one of the four biggest prizes in their sport.
"Look, it's fairly obvious that all tennis players are playing tennis for the Slams," said Zverev, the runner-up to good pal Dominic Thiem at last year's US Open. "Obviously, the Grand Slams are the tournaments that we want to win the most. Before, maybe, the last few years, I was putting too much pressure on myself. ... Before Medvedev and Tsitsipas arrived, I was seen as this guy that was going to all of a sudden take over the tennis world.
"I was putting pressure on myself, as well,'' Zverev continued. "I was not very patient with myself, which I feel like now, maybe, I learned how to deal with the situation a little bit better.''
He showed that quality at a key juncture Tuesday. Zverev did not want to believe that Davidovich Fokina had saved a break point with a shot that landed on -- or was it merely near? -- a line in the fourth game. Zverev crouched down near the mark on the red clay and engaged in a bit of an argument with chair umpire Alison Hughes, repeatedly saying, "No!'' and then ``How?''
Hughes, whose call was backed up by an unofficial video rendering shown on TV, didn't budge, and Zverev quickly lost that game, then the next one, too, to fall briefly behind. Could have been the start of an unraveling. Instead, Zverev grabbed 16 of the remaining 19 games.
"I'm maybe a little bit calmer at the tournaments,'' he said. "But the end goal hasn't changed.''
For Tsitsipas, who goes into Friday with an 0-3 mark in Slam semifinals, the key moment came late in the second set. Medvedev, who suddenly found his footing on clay this year after arriving in Paris with an 0-4 career record at the French Open, sort of snapped to and made things interesting.
Indeed, Medvedev made so much headway that he held a pair of set points after Tsitsipas dumped an overhead into the net and was forced to serve at 15-40 while trailing 5-4. But Medvedev let Tsitsipas out of the predicament with a bad return of a second serve, followed by a flubbed forehand, and soon enough it was 5-all. Less than 15 minutes later, Tsitsipas hit a swinging forehand volley winner to close out that set and was on his way to his second win in eight career meetings against Medvedev.
"To be honest, the biggest difference was the surface,'' Medvedev said, "but when I say this, I finally do not say it in a way, 'Oh, I cannot play on clay! Mamma mia!' or whatever. It's just that his shots were better on clay.''
While Medvedev briefly led by a break in the third, Tsitsipas pulled even, then broke after being down 40-love in the last game. He closed his victory with a passing shot winner off a return when Medvedev charged the net behind an underarm serve on match point.
"Didn't work out at all,'' Medvedev said. Tsitsipas' take? He called it "a very millennial shot.``