The duo could face each other at the quarter-final stage.
Thursday's match was just Venus Williams's seventh of the year and first since January's Australian Open, where she fell to Simona Halep in the round of 32.
Defending Olympic champion Andy Murray reached the semi-finals of the men's tennis on Friday after winning a third-set tiebreak to scrape through a testing encounter against American Steve Johnson.
Djokovic, the ninth seed, was originally scheduled to play Australian Open semi-finalist Chung Hyeon but the 22-year-old South Korean withdrew with a back injury about an hour before the match was due to start.
Summary of sports events and persons who made news on Saturday
The 30-year-old is the first German woman to win Wimbledon since Steffi Graf in 1996.
The top women's seeds continued to be scattered at Wimbledon on Wednesday, with Caroline Wozniacki's exit meaning five of the top eight were gone before the end of the third day.
Wimbledon champion Garbine Muguruza suffered a 6-2, 6-4 defeat at the hands of unseeded Czech Barbora Strycova in the second round of the Nature Valley Classic in Birmingham on Thursday.
Ferrer, 37, announced earlier in the year he would end his 19-year career at the Madrid Open and prolonged his time on court by a day by beating Roberto Bautista Agut on Tuesday, but was easily overpowered by world number four Zverev.
Eleven-times champion Rafael Nadal booked his place in the semi-finals of the Barcelona Open semi-finals by beating German Jan-Lennard Struff 7-5, 7-5 in a hard-fought match on Friday.
Angelique Kerber showed more passion in the media centre than on the court when she crashed out of last year's WTA Finals, the German angered by the format and frustrated by her inability to win the set off an eliminated opponent she needed to advance.
World number one Rafael Nadal recorded his 20th straight win on clay as he began his quest for a sixth title in Madrid, defeating Frenchman Gael Monfils 6-3, 6-1.
Madison Keys beat fellow American CoCo Vandeweghe for the second time in eight days with a 6-4, 3-6, 6-3 victory on Monday to reach the second round of the Cincinnati Open.
Triple Tour de France champion Chris Froome says he has "no issue" with his private medical records being leaked in a cyber attack by Russian hackers on the World Anti-Doping Agency (WADA).
Timea Bacsinszky wants a lasting souvenir at the French Open.
A summary of sports events and sports persons, who made news on Sunday
Serena Williams and defending champion Maria Sharapova remained on course for a heavyweight Madrid Open final.
Roger Federer is keeping a lid on expectations.
Canadian Milos Raonic declared that he would stop at nothing to win a major title after admitting his straight sets loss to Andy Murray in Sunday's Wimbledon final would sting.
The peak remains tantalisingly close for Serena Williams but negotiating the final incline to a record-equalling 22nd Grand Slam singles title is proving the trickiest of all.
'Everyone always talks about how hot Melbourne is but the US Open's way worse'
Images from Day 3 of the 2020 US Open in New York, on Wednesday.
Greek teenager Stefanos Tsitsipas secured the biggest win of his career when he sent Wimbledon champion Novak Djokovic packing in the third round of the Rogers Cup with a stunning 6-3, 6-7(5), 6-3 win on Thursday.
While some say the five-times Grand Slam champion, initially banned for two years after testing positive for Meldonium, has done her time some fellow players are angry the red carpet is being rolled out.
Photos from French Open matches played at the Roland Garros on Friday
Serena Williams must navigate a heavily American quarter of the draw including sister Venus to complete a calendar sweep of the four Grand Slams, while two sensational quarter-finals loom on the men's side after Thursday's U.S. Open draw.
World No 1 Serena Williams beat Agnieszka Radwanska for the eighth time in eight matches to move ominously towards the semi-finals of the WTA Championships on Wednesday.
Images from Day 4 of the Wimbledon tennis championships played in London, on Wednesday.
World No 2 Rafael Nadal sailed into the quarter-finals of the China Open, his first tournament in 13 weeks, with a 6-3, 6-4 win over German qualifier Peter Gojowczyk on Thursday.
World No 1 Serena Williams and Serbian eighth seed Jelena Jankovic set up a final showdown in the China Open after their contrasting victories in the semi-finals on Saturday.
IMAGES from the matches played on Day 2 of the Wimbledon Lawn Tennis Championships at All England Lawn Tennis and Croquet Club on Tuesday.
2014 Wimbledon finalist Eugenie eliminated in 1st round.
As tradition demands the Serb will open play on Centre Court on Monday as defending men's champion but rather than a gentle loosener the 28-year-old faces a real danger in the form of Germany's Philipp Kohlschreiber, the world number 33.
Marin Cilic and Milos Raonic booked their spots in the Paris Masters second round on Monday, while Roger Federer pulled out of the tournament with next month's ATP Finals on the horizon.
Serbia's Novak Djokovic is the top seed in the men's draw which includes five-times US Open champion and 17-times Grand Slam winner Roger Federer as seventh seed - his first time the Swiss has been placed outside the top three in a Grand Slam in over ten years.
A tenacious Roberto Bautista Agut battled back to beat world number one Novak Djokovic 1-6, 7-5, 6-3 and advance to the quarter-finals of the Miami Open on Tuesday as the Spaniard claimed his second win over the Serb this year.
Reigning champions Novak Djokovic and Serena Williams have been named top seeds for the Australian Open starting on Monday.
IMAGES from matches played on Day 4 of the French Open at Roland Garros on Wednesday
Simona Halep will take over as the new number one in the WTA world rankings after progressing to the China Open final with a dominant 6-2 6-4 victory over Latvia's Jelena Ostapenko in Beijing on Saturday.
Nadal needed all his experience to keep Pouille at bay in the decider and the match looked to be heading for another tiebreak before he pounced to break Pouille's serve for the first time to go 6-5 up in the third.