Miami Open: Aryna Sabalenka beats Caty McNally to reach last 16
Zheng beat American 15th seed Madison Keys to claim her first win over a top-20 player since having elbow surgery in July.
Sabelenka has won seven of her eight meetings with Olympic champion Zheng.
Third seed Elena Rybakina cruised into the last 16 with a 6-3 6-4 victory over Ukraine’s Marta Kostyuk.
Kazakhstan’s Rybakina will play Australian qualifier Talia Gibson, who knocked out another seeded player courtesy of a 6-2 6-2 win over 18th seed Iva Jovic.
Gibson, who reached the Indian Wells quarter-finals, beat former world number one Naomi Osaka in the second round in Miami.
Fifth-seeded American Jessica Pegula, runner-up to Sabalenka last year, needed only an hour and six minutes to beat Canada’s Leylah Fernandez 6-2 6-2.
Latvia’s Jelena Ostapenko, runner-up in Miami in 2018, fought back to claim a 5-7 6-2 7-5 win over seventh seed Jasmine Paolini of Italy.
Ostapenko will next play American world number 45 Hailey Baptiste, who beat Ukrainian ninth seed Elina Svitolina 6-3 7-5.