Meanwhile, in women's action, Maria Sharapova crashed out in the semifinals of the Birmingham grass-court event, beaten in straight sets by China's Li Na.

CNN: Injured Roddick misses out on Murray final

Earlier, unseeded Clijsters beat China's Li Na in straight sets to continue her incredible comeback to tennis after a two-year layoff.

CNN: Wickmayer moves into final four at U.S. Open

Zheng's compatriot Li Na followed her into the quarterfinals on Monday after stunning fourth-seeded Dane Caroline Wozniacki in straight sets.

CNN: Tennis: Henin battles into semis