Zheng’s only win in eight previous meetings against Swiatek was in the semi-finals of the 2024 Olympics on her way to singles gold in Paris.
She will discover her quarter-final opponent later on Monday, when former US Open champion Osaka plays second seed Rybakina.
The most recent qualifier to reach this stage of the women’s draw at the US Open was Great Britain’s Emma Raducanu, who went on to win the title in 2021.
And Zheng is not the first female qualifier to perform well at a Grand Slam in 2026 – Poland’s Maja Chwalinska, who began the French Open at 114th in the world, lost to Russian teenager Andreeva in the final at Roland Garros.
For Swiatek, 25, a fourth-round exit is a disappointing end to her Grand Slam season, with a quarter-final appearance at the Australian Open her best result.
She was beaten in round four of the French Open, while the defence of her Wimbledon title ended in the third round.
It means that, for the first time since 2021, Swiatek will end a year without winning one of the sport’s four majors.
Swiatek, who received treatment to her left thigh when leading 2-1 in the second set, had entered the US Open in excellent form by winning the WTA 1000 event in Toronto and getting to the semi-finals in Cincinnati, while she had progressed through to round four without dropping a set.
