The top seed from Belarus won 7-6(3), 6-3 against the Chinese eighth seed. She fought back after struggling in the first set against Zheng, who had beaten her in the last eight on clay in Rome last month.
"The last tournament I was pretty exhausted," said Sabalenka. "Today I was more fresh I was ready to battle, to fight and give everything."
"Honestly, I was actually glad that I lost that match because I needed a little break before Roland Garros."
Sabalenka faced a tough test against Zheng, who had been on a winning streak of 10 matches on the Paris clay after her run to Olympic gold last year.
The Chinese player broke and led 4-2 in the first set. But numerous unforced errors - 31 in total - allowed the Belarusian to come back.
The second set was also tight before Sabalenka broke back to lead 4-3, taking advantage of her opponent's errors.
Sabalenka converted her first match point on a poorly controlled drop-shot from Zheng to reach her seventh semi-final of the season.
Sabalenka advances to her 11th major semi-final overall, and her second in Paris following her run in 2023, which ended in a three-set loss to Czech Karolina Muchova.
"I think we are all here for one reason, everyone wants that beautiful trophy," said Madrid Open winner Sabalenka.
"I'm really glad that I have another opportunity, another semi-final, to do better than I did last time. I'm ready to go out there and fight and compete for every point."
A three-time Grand Slam winner, winning the Australian Open in 2023 and 2024 and the reigning US Open champion, Sabalenka is chasing her first title in Paris.