Trailing 5-4 in the first set, Zheng rolled to a 7-5, 6-0 victory in 77 minutes. The reigning Olympic gold medalist will next face No. 8 seed Leylah Fernandez of Canada.
Third-seeded Daria Kasatkina of Russia rallied for a 3-6, 6-3, 6-1 win over McCartney Kessler. Kasatkina will take on Sofia Kenin, who outlasted Denmark's Clara Tauson 6-7 (8), 6-4, 7-6(6) in 2 hours and 51 minutes. No. 9 seed Katie Boulter of Great Britain crushed Japan's Kyoka Okamura 6-1, 6-2 in 69 minutes.
Guangzhou Open
Top-seeded Czech Katerina Siniakova avoided the upset bug with a swift 6-1, 6-4 victory against Alycia Parks in China.
Siniakova saved all seven break points she faced and converted four of five break chances in the 78-minute win. Her opponent in the quarter-final will be Bernarda Pera, who rolled to a 6-2, 6-2 win against China's Shuai Zhang.
Siniakova's compatriot, No. 2 seed Marie Bouzkova, was not as fortunate and lost to Caroline Dolehide 6-7(3), 6-4, 7-6(6) in 3 hours and 18 minutes. Thailand's Manachaya Sawangkaew wiped out No. 3 Yue Yuan of China 6-2, 6-3 in just 67 minutes.