Williams defeated Russia's Margarita Gasparyan 6-2, 6-4 while Kenin needed an hour and 22 minutes to maneuver past Canadian youngster Leylah Fernandez 6-4, 6-3.
Medvedev will next face fellow American Frances Tiafoe, and Thiem will take on Canada's rising star Felix Auger-Aliassime.
In the other two matches of the day, Hunan Hualai edged Shenzhen Nankeda 3-2, while Olympic champion Chen Long led Xiamen Tefang to a win over Anhui Souyu 5-0. Enditem
"Right now I'm really focused on the US Open, and nothing else I can think about right now," said Williams, who won six of her 23 Grand Slam singles titles at the US Open.
"It was a delight to wear yellow. Hopefully I'll keep for a few more days. Let's first see how it goes tomorrow."
"I'm very happy to play a tough game with such wonderful shuttler. I was not cautious enough today and I felt nervous on some key points. But generally I think I performed well," said Chen.
Over 260 contestants from six Chinese teams participated in six competitions, including the tank biathlon. Enditem
"But we are optimistic because we know we can do it because we have a fantastic partnership with Tokyo and an equally strong partnership with Beijing," he added.
SYDNEY, Sept. 8 (Xinhua) -- Women's world number one Ashleigh Barty will not compete at the French Open later this month, citing COVID-19 risks and a lack of preparation.
"Ensuring a safe return to international table tennis has been our utmost priority ever since the pandemic broke out. We have managed to get events back up and running before the end of 2020," ITTF president Thomas Weikert said. Enditem
Liang Weikeng/Zheng Xuhui moved past Dong Weijie/Ni Bowen in the mixed doubles to overtake the lead for Shenzhen, while Han Qianxi overwhelmed Zhang Yiman in the women's singles to level for Zhejiang.