Alejandro Davidovich Fokina

Last year's runner-up Andrey Rublev, however, missed out on a last-eight spot after falling to a three-set defeat against Jannik Sinner.

World number three Zverev overcame Spain's Pablo Carreno Busta 6-2 7-5 to progress in Monaco, where he is seeking to win the sixth ATP 1000 title of his career.

"For the second clay-court match of the season, I can't complain too much," the 24-year-old second seed said on court after sealing the victory.

"Yes, I lost focus a little bit in the second set, but at the end of the day, he's somebody that can really play. I'm happy with a two-set win."

Tsitsipas (3) remains in contention for a second consecutive title in the principality after defeating Laslo Dere 7-5 7-6 (7-1) and will face off against 12th seed Diego Schwartzman for a semi-final spot after the Argentine defeated Lorenzo Musetti in a hard-fought three-set encounter.

There will be no repeat of 2021's final between Tsitsipas and Rublev, however, after the Russian fell to a thrilling 5-7 6-1 6-3 loss to ninth seed Sinner in the day's final contest.

The other seed to fall victim to a shock in the last 16 was world number seven Casper Ruud, losing 6-3 7-5 to Grigor Dimitrov, who will face Poland's Hubert Hurkacz in the last eight. 

Finally, Novak Djokovic's conqueror Alejandro Davidovich Fokina cruised past David Goffin 6-4 6-1 to set up a quarter-final tie with the United States' Taylor Fritz, who bested compatriot Sebastian Korda – with whom he played doubles with in Monte Carlo – in straight sets.

Zverev, who is ranked third in the world - two places higher than Tsitsipas - fought back to defeat Jannik Sinner 5-7 6-3 7-6 (7-5) in his quarter-final match, denying his opponent another top-five seed scalp following his prior win over Andrey Rublev.

"It means a lot, definitely, especially [with] how this year has been going so far for me," said Zverev after a gruelling three hours on court.

"I've lost long matches like that, so I’m happy I won this one."

Tsitsipas also orchestrated a superb turnaround against Diego Schwartzman, prevailing 6-2 6-7 (3-7) 6-4.

The Greek had looked set for a last-eight exit at four games down in the final set, only to stage a dramatic comeback to keep his hopes of a first title since last May's Lyon Open alive.

"There was a moment in the match where I felt what I was doing wasn't working," Tsitsipas said.

"He had a massive lead and momentum in what he was trying to do. I just tried to stay in the match as much as I could and that worked out very well.

"I wasn't expecting much at that point being a double break down, so I relaxed at that point."

Schwartzman meanwhile will rue his inability to put the tie to bed, having already reached two ATP finals this year.

Grigor Dimitrov and Alejandro Davidovich Fokina will face off in the other semi-final.

Bulgarian Dimitrov beat off Hubert Hurkacz in another final-set tie-break, winning 6-4 3-6 7-6 (7-2).

Fokina, who eliminated Novak Djokovic in the second round, turned over Indian Wells champion Taylor Fritz in another comeback result, triumphing 2-6 6-4 6-3.