The 595th-ranked Zhang Shuai, who earlier this week won her first match in more than 600 days, stunned US Open semi-finalist Emma Navarro 6-4, 6-2 in Beijing on Friday.
The 35-year-old Zhang reached round three of the China Open, where she is the lowest-ranked player to ever compete in the main draw of her home tournament.
On Wednesday, Zhang won her first singles match since January 2023 to snap a painful run of 24 defeats on the WTA Tour.
Coming into the prestigious WTA 1000 event as a wildcard, the former top-25 player defeated the 65th-ranked American McCartney Kessler in straight sets.
Zhang, a two-time Grand Slam quarter-finalist who has been plagued by injuries, repeated the feat with a surprise victory over the American sixth seed Navarro.
Zhang, who has won two Grand Slam doubles titles, faces the 28th-seeded Russian Anastasia Potapova or Belgium's Greet Minnen next.