Story so far: Zverev books Davidovich Fokina last-eight date

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Alexander Zverev, Roland Garros 2021, fourth round© Nicolas Gouhier/FFT
 - Reem Abulleil

Sixth-seeded German Alexander Zverev has knocked out former world No.4 Kei Nishikori for a third consecutive tournament to become just the second German man -- behind Boris Becker -- to reach at least three Roland-Garros quarter-finals.

Zverev, who is now 5-1 overall against Nishikori and has defeated the Japanese player in Madrid and Rome last month, posted a 6-4, 6-1, 6-1 win on Sunday in a night-session showdown on Court Philippe-Chatrier in less than two hours.

The 24-year-old Zverev has made the last-eight stage in Paris three times in the last four years and will next take on Spaniard Alejandro Davidovich Fokina, with both of them chasing a maiden semi-final at Roland-Garros.

Zverev was a runner-up at the US Open last September and won the Madrid title in the build-up to this fortnight.

Rybakina shocks Serena

Kazakhstan's Elena Rybakina claimed the biggest Grand Slam victory of her career by ousting 23-time major winner Serena Williams 6-3, 7-5 in the Roland-Garros fourth round.

The 21-year-old is through to the quarter-finals at a Slam for the first time, and she has done it without dropping a set so far this fortnight in Paris.

Williams, a three-time champion in Paris, reached the fourth round on her Roland-Garros debut in 1998, one year before Rybakina was born.

The American's search for an elusive record-equalling 24th Grand Slam trophy continues, while Rybakina moves on to face No.31 seed Anastasia Pavlyuchenkova.

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Rybakina's win over the seventh-seeded Williams is her first top-10 win at a major and fifth overall.

"I'm so happy with my match today, it was amazing and thank you so much for coming to watch today," said the No.21 seed, who is contesting just her second Roland-Garros main draw.

"Of course I was nervous, even in the last game, I was not serving that well before, but I'm just happy that I managed to with my thoughts and everything and I won today."

New milestone for ADF

An emotional Davidovich Fokina could barely speak during his on-court interview with Cedric Pioline after he reached his maiden Grand Slam quarter-final with a gruelling 6-4, 6-4, 4-6, 6-4 victory over Argentinian lefty Federico Delbonis.

The 22-year-old Spaniard hit 42 winners against 47 unforced errors during the three-hour affair and takes a 0-2 record into his clash with Zverev.

"I worked hard for this moment, and thanks to my team, they are supporting me every day. A lot of emotions... I'm so happy," said the world No.46.