The Chinese 23rd seed had never previously gone past the fourth round of a Grand Slam and hopes her quarterfinal appearance at Flushing Meadows is a career milestone despite losing 6-1 6-4 to second seed Aryna Sabalenka.

"There is still a lot of room for me to improve, especially she make me think a lot, once again, that I have to go back and put some work (into) my tennis," said Zheng.

She won her maiden title on the WTA Tour in July in Palermo, shortly after she began working with coach Wim Fissette, a veteran who counts major winners Naomi Osaka, Victoria Azarenka, Angelique Kerber and Kim Clijsters among his former clients.

"I was kind of impressed by her, first of all, like the athlete she is. It's very impressive, strong and really fast on the court," Fissette told reporters.

"Also really explosive, and you see that in her strokes, like, big serve, big forehands. Lots of possibilities. But also still pretty raw."

The partnership looked like it was paying off in New York as she beat last year's runner-up Ons Jabeur in the fourth round, her first win over a top-10 player at a Grand Slam.

Zheng flummoxed opponents with her heavy spin forehand that has quickly become a signature weapon and delivered a tournament-high 28 aces on the way to the last eight.

Fissette said the plan was to fine-tune her decision making.

"On the (hardcourt surface) I still feel like she's looking to understand who she really is and to use her strokes like the best possible way with the right strategy," he told reporters.

"Plan A should be, like, controlling the point from the serve or from the return, and plan B is definitely with her speed and also, like, her defensive skills should also be super consistent."