A disciplined performance saw Zheng swatted aside in little over an hour on a gusty afternoon in Osaka. Service breaks bookended the first set before the American, seeded No.6 this week, raced through the second and into a last four meeting with 2009 champion Samantha Stosur.
"I think I just played a pretty solid match overall," Keys said. "It was definitely windy and I wasn't able to hit as many big serves as I was yesterday as I was trying to play the percentages a bit more. The conditions are just something you have to learn to deal with, I just tried to keep moving my feet and judge when to go for it."
Keys has been in fine form in her opening three matches - she is yet to drop a set - but admits her game is still a work in progress. "I've played a lot of matches this year and I try to take something from each one - not just wins, but also losses. I'm just trying to get better each time and always trying to find new things to work on after each match."
Stosur's passage through was not quite so serene, overcoming a mid-match fightback and a partisan crowd to see off Japan's Misaki Doi, 61 36 63.
Since her victory in Carlsbad in August, Stosur has struggled to find her best tennis, and after a bright start was made to dig deep against Doi.
"She made lots of errors in the first set and didn't really make me do so much, but in the second she played much better. I didn't really adjust to this and then she played a very good game to break my serve and then all of a sudden the set was over."
The third was a similarly competitive affair, however, this time it was Doi who faltered, double faulting to gift the decisive break to Stosur in the penultimate game.
Stosur prevailed in two tight sets the last time she met Keys, earlier this year in Indian Wells, and is well aware of the challenge that awaits her on Saturday. "I know her a little bit - we played in Indian Wells this year - she's tall, very strong, has a very big serve and hits the ball hard.
"It's going to be a very tough match and I'm going to have to serve well because she can make it difficult when you're behind in the set."
On the other side of the draw, wildcard Kurumi Nara made her maiden WTA semifinal, and kept hopes of a Japanese champion alive, with a 76(4) 26 61 victory over Polona Hercog. Meeting her for a place in the final will be the in-form Eugenie Bouchard, who came back to defeat Barbora Zahlavova Strycova, 26 64 61, to reach her second semifinal in the past month.