Qinwen, ranked No 7, will play Russian Diana Shnaider, the No 6 seed, for a place in the final. It will be the first meeting between the two players.
Ahead of her win today, the 22-year-old Chinese won against Japanese Moyuka Uchijima (7-5, 6-0). It has been a successful Asian swing for her, having reached the semi-finals in Beijing and the final in Wuhan. Zheng has already qualified for the season-ending WTA Finals for the first time in her career.
Fernandez, ranked No 35, benefited from the retirement of Belarusian lucky loser Aliaksandra Sasnovich (5-7, 6-2, 5-2) and edged out Frenchwoman Varvara Gracheva (6-0, 3-6, 7-5) earlier in the week.
Tokyo WTA 500, other quarter-final results (Ariake Coliseum, hard, USD 922.573):
- Diana Shnaider beat Sayaka Ishii (walkover)
- Sofia Kenin (WC) beat Daria Kasatkina (3): 6-3, 6-4
- Katie Boulter (9) beat Bianca Andreescu (WC): 6-2, 6-1