Against Djokovic, his sliding across the court was almost flawless, as was his ability to disguise his angles until the last moment in what was perhaps the match of the tournament so far.
The Serbian, who is not committed to any event before The Championships, commented: 'I don't know if I'm going to play on grass.
"Is good for my opponent in Wimbledon", he said.
"It was an awesome, high level match", said Zverev.
Keys, the US Open runner-up past year, will face either Czech 26th seed Barbora Strycova or Yulia Putintseva, the 98th-ranked Kazakh, for a place in the semi-finals. "So I'll approach it very seriously".
Djokovic saluted Cecchinato who he warmly embraced at the net.
"He played incredible and credit to him".
"I struggled at the beginning and also had a little injury at the beginning".
"It's a pity I could not capitalize on the chances I had", Djokovic said.
Keys had always struggled on clay before this year, but has now reached the last eight at all four Grand Slams after impressively cruising through the draw without dropping a set. "There was another year of work where I improved and developed my game", said the 24-year-old.More news: US televangelist appeals for donations for $54 million private jet
He made Djokovic pay for that failure to convert when he reeled off four successive points in the ensuing tiebreaker.
Playing at his lowest ranking for nearly 12 years after months of struggling with an elbow injury and indifferent form, Djokovic has made the last eight by dropping just one set.
While that was happening, Cecchinato was docked a penalty point for unsportsmanlike conduct after a lengthy argument with the umpire and supervisor for leaving the court without permission.
Zverev produced some stunning tennis in the closing stages of a dramatic fourth-round victory and will next face Dominic Thiem who reached a third successive quarter-final in Paris by seeing off Japan's Kei Nishikori 6-2, 6-0, 5-7, 6-4.
But Zverev, as he did in his wins over Dusan Lajovic and Damir Dzumhur, forced a decider, sealing the set with an ace after saving two break points.
Dimitrov tried to be competitive in the second set but failed miserably.
No. 10 Sloane Stephens finds herself up against No. 14 Daria Kasatkina, who lost some rest after Sunday's match was postponed in the second set due to darkness.
"Then once you get to the second week, every match obviously has more nerves, and there's more on the line and all of that".
The statistics made bleak reading for Zverev - he finished with 42 unforced errors and just 19 winners.