After a discussion of around 10 minutes between tournament referees and officials, Djokovic was disqualified from the match.
Williams will take on Bulgaria's Tsvetana Pironkova, who overcame Alize Cornet of France 6-4, 6-7 (5), 6-3 in another round of 16 match.
It is the second such injury in eight months for Zaniolo, as the 21-year-old was stretchered off in the Serie A game between Roma and Juventus in January, following a tackle with Adrien Rabiot and Matthijs de Ligt.
The second chance for Hebei came in the stoppage time. In the 96th minute, Samir Memisevic made a direct pass forward, gifting Brazilian striker Marcos Vinicius Amaral Alves an easy tap-in to seal the victory.
With reigning US Open champion Nadal, who cited concerns about traveling amid the COVID-19 pandemic, and an injury-hit Federer opting out of the event, Djokovic had been favorite to win another title in New York. Enditem
WADA president Witold Banka said the Agency would follow the representatives' suggestions.
According to WADA, government representatives have asked the Agency to consider the possibility of amending its rules so that such a move could face potential sanctions.
Djokovic's exit means there will be a first-time Grand Slam champion in the men's draw, with Zverev among the contenders at Flushing Meadows.
"I'm happy for the mentality, the performance, the boys really played brilliantly," Mancini told Italian broadcaster Rai.
Fans of Guangzhou Evergrande cheer for the team during the 9th round match between Guangzhou Evergrande and Guangzhou R&F at the postponed 2020 season Chinese Football Association Super League (CSL) Dalian Division in Dalian, northeast China's Liaoning Province, Sept. 4, 2020. (Xinhua/Pan Yulong)
"I have a good impression about China. It's different from what you hear in Europe," Onuegbu said.