Zhang dropped just four games as she blew away the 13th seed 6-3, 6-1 at Beijing's National Tennis Center.

Her victory over the 2017 US Open champion was particularly sweet as China celebrates National Day on October 1 every year.

"This is the best National Day ever, with a victory, my first time into the third round of the China Open," the 25-year-old said. 

"I felt like I had nothing to lose today. 

"I did not want to regret my performance on such a special day. 

"My mom was here in the stands - it was a gift to my motherland as well as my mom."

The women's China Open tournament is a Premier Mandatory event on the Women's Tennis Association circuit.

Zheng, the world number 39, won her first Premier event in August at the Silicon Valley Classic in San Jose, California.

She will now play world number one and top seed Ashleigh Barty in the last-16 after Australia's French Open champion knocked out Kazakhstan's Yulia Putintseva 6-4, 6-2.

Japan's fourth seed Naomi Osaka, the former world number one, breezed through as the double grand slam champion routed German qualifier Andrea Petkovic 6-2, 6-0.

There was another shock as Germany's 10th seed Angelique Kerber, a three-time grand slam winner, was beaten 6-4, 6-2 by Slovenia's Polona Hercog.

Two-time Wimbledon champion Petra Kvitová did advance, however, with the Czech player seeing off France's Kristina Mladenovic 6-4, 6-4.

Round-three matches are tomorrow.