BANGALORE, India — Unseeded Chinese Yan Zi shocked top-seeded Jelena Jankovic of Serbia 6-3, 3-6, 6-today to enter the semifinals of the $600,000 WTA Tour's Bangalore Open.

"This is one of the best wins of my career, it's been a dream run," said Yan, who defeated eighth-seeded Maria Kirilenko of Russia in the opening round.

Yan's semifinal opponent will be fourth-seeded Swiss Patty Schnyder, who faced a strong challenge before downing Uzbekistan's Akgul Amanmuradova 4-6, 6-4, 7-6 (1) in the quarterfinals.

The Williams sisters — second-seeded Venus and third-seeded Serena — set up a semifinal encounter with comfortable victories against their Russian opponents Friday.

Venus Williams cruised past Vera Zvonareva 6-4, 6-3, while Serena Williams outplayed Anastasia Rodionova 6-1, 6-4.

World No. 4 Jankovic struggled with her service as Yan seized control of the match.

Yan clinched the first set by breaking Jankovic in the eighth game. Jankovic claimed the second set by effecting service breaks in the fourth and sixth games.

The decider set saw the top seed struggling to hold serve as Yan raced away to a 4-0 lead before being broken.

"I was struggling with my service in the first set. Then my shoulder began troubling me after the second set. I hope the injury is not serious," said Jankovic.

Yan said she was hoping to repeat her fine show with Schnyder in the semifinal.

Venus Williams raced to a 5-1 lead in the first set, but Zvonareva responded with two breaks of her own to square the set before the American broke in the 10th and final game.

In the second set, Williams forced two breaks while dropping serve once in claiming victory over her Russian opponent.

"It was difficult to play Venus today," said Zvonareva. "I have a lot of work to do. I have not been at my best form and need to get better."