Rains disrupted the action in the final Grand Slam event of the year, and most of the scheduled matches in the women's draw were postponed until Thursday.
Those matches included Serena Williams' second career meeting with Galina Voskoboeva. Williams, seeking her ninth tournament title of the year, lost only one game in her first-round match against former French Open champion Francesca Schiavone.
Zheng advanced to a third-round meeting with No. 18 seed Carla Suarez Navarro, who took out American Coco Vandeweghe 6-3, 6-4.
Radwanska, seeded third and the runner-up last year at Wimbledon, recorded a 6-0, 7-5 win over Maria-Teresa Torro-Flor.
Anastasia Pavlyuchenkova awaits Radwanska in the third round after storming past Australian Ashleigh Barty 6-4, 6-0.
Li, the No. 5 seed, was a 6-2, 6-2 winner over Sofia Arvidsson and will now face Briton Laura Robson, who ousted Caroline Garcia 6-4, 7-6 (7-5).