In men's draw, second seed Dominic Thiem of Austria celebrated his 27th birthday by notching a comfortable 6-3, 6-3, 6-2 second-round victory over India's Sumit Nagal.
She will take on 15th-seeded Maria Sakkari of Greece in the last 16, who stunned Williams at last month's Western & Southern Open.
Looking at the potential of his young front line, optimism seems appropriate.
"There's going to be a new Grand Slam champion. That's all I know right now. There's no past Grand Slam champions left in the draw," Zverev said.
In the other two matches of the day, Hunan Hualai survived an intense battle to overcome Xiamen Tefang 3-2, while Jiangsu Weikeduo lost to Zhejiang Nengyuan 4-1, and remain at the bottom with no wins. Enditem
"It really hurt me that people could think I would be able to go to court against Barcelona for my own benefit. I would never do something like that," commented the striker.
"For the many, many people who have been asking how I am, this morning I underwent medical checks that revealed a tear of the cruciate ligament in my left knee," he wrote.
In the Suzhou Division, Teda sits at the bottom, while Chongqing ranks sixth. Enditem
In other games in the top-tier League A, Portugal beat Croatia 4-1 thanks to goals by Joao Cancelo, Diogo Jota, Joao Felix and Andre Silva. Portugal were missing Cristiano Ronaldo, who was out because of a toe infection.
"He's a very solid player, maybe doesn't possess any big weapons, but every shot is very good," Djokovic said of Busta. "He returns a lot of balls, so I've got to be ready for a lot of exchanges. It's going to be a demanding match physically and mentally. Hopefully I'll be able to continue the good performance that I had tonight."
European champion Laura Muir was unstoppable in the women's 1,500m, continuing her momentum following a big win in Oslo two weeks ago. The Briton clocked 3:58.24, followed by Sofia Ennaoui of Poland and Romania's Claudia Bobocea.