"I never think I can (reach) the semifinal," said Zheng, who is playing at Wimbledon for only the third time and will next face two-time champion Serena Williams.
Zheng landed 65 percent of her first serves in the match, while Vaidisova struggled with hers and was broken five times. It was only in the second set that Vaidisova got her serve working properly.
"Nicole had the big serve," Zheng said. "The second set I felt I had some small chance but she ... played more aggressive."
Zheng has only won three titles on the WTA Tour in her career, and her best previous Grand Slam performance came at the 2004 French Open when she reached the fourth round.
At Wimbledon, she reached the third round in 2006 but missed last year's tournament with a left ankle injury.
Vaidisova reached the fourth round at the Australian Open but was eliminated in the first round at the French Open. The 19-year-old Czech has twice reached the semifinals at a Grand Slam, the 2006 French Open and the 2007 Australian Open.
Her best previous showing at the All England Club came last year when she reached the quarterfinals.
Vaidisova is one of only six women to have won five tour titles before her 17th birthday, following Tracy Austin, Andrea Jaeger, Monica Seles, Jennifer Capriati and Martina Hingis.
