Hsieh beat Kurumi Nara of Japan 6-7, 6-3, 6-4 in a match lasting 2 hours, 42 minutes. She had only a few hours of rest before defeating China's Zhang Shuai 6-2, 6-2. The Taiwanese player completed her first- and second-round matches on the same day after thunderstorms disrupted play earlier this week.
Patricia Mayr-Achleitner of Austria won 6-3, 6-2 against Wang Qiang of China, who ousted top-seeded Caroline Wozniacki in the first round.
Others moving into Friday's quarterfinals are fourth-seeded Ayumi Morita of Japan, wild card Bethanie Mattek-Sands of the U.S., Karolina Pliskova of the Czech Republic, Luksika Kumkhum of Thailand, Ashleigh Barty of Australia and Anastasia Pavlyuchenkova of Russia.