His opponent, however, was the stronger in an epic fourth-set tiebreak, prevailing 6-3 7-6 (4) 1-6 7-6 (11) on his fourth match point after more than three hours of high-octane tennis.
The last of his 12 majors was secured at Roland Garros in 2016 when he completed a career Grand Slam.
Zverev is playing in a quarter-final at the Slams for the first time while Thiem has made the semi-finals in Paris for the last two years.
"I definitely need to take some time off now to kind of reassess the whole clay-court season, to be honest", said Dimitrov. I just came from the court.
The tennis star was charged with match fixing and prohibited match betting.
"Maybe I'm sleeping. It's incredible, it's unbelievable for me".
Djokovic, who lifted the title at Roland Garros in 2016, had numerous opportunities to level the match during the fourth set.
"He played wonderful, so congratulations for a great performance", he said.
"Well, I'm young, so I might as well stay on court, get some practice and entertain you guys", smiled Zverev, who is bidding to become the first German man to win the French Open since 1937.
Former world number one Djokovic will face Italian surprise package Marco Cecchinato in his 40th major quarter-final.
When he qualified for the last eight at the French Open, Marco Cecchinato said it was the happiest day of his life.
"I'm a better player in general, for sure".
"First week, my goal is to get to the second week", said 23-year-old Keys.
"I knew I'm not going to win the match".
Keys's close friend Sloane Stephens, the US Open champion, takes on Russia's Daria Kasatkina who put out Wozniacki. Stephens beat Keys in the U.S. Open final last September, and their rematch on Thursday will be the first all-American women's semifinal at the French Open since Serena Williams defeated Jennifer Capriati in 2002.
It's incredible to think the 25-year-old came to Paris having never won a Grand Slam singles match given his form.
World number 98 Yulia Putintseva, a quarter-finalist two years ago, tackles Madison Keys of the United States.
Cecchinato, who described his sporting heroes as the Brazilian footballer Kaka and Marat Safin, is the first Italian man to reach a Grand Slam semifinal since Corrado Barazzuti made the last four here in 1978. He just held his nerves amazingly well in the important moments. "It feels completely different here".