* China's Zheng upsets former champion Sharapova
* Easy passage for Wozniacki and Dementieva
(Adds late match)
INDIAN WELLS, California, March 14 (Reuters) - Former champion and 10th seed Maria Sharapova of Russia was knocked out of the Indian Wells WTA tournament on Sunday, losing an error-strewn marathon to China's Zheng Jie 6-3 2-6 6-3.
While Sharapova made a premature exit, it was plain sailing for second-seeded Dane Caroline Wozniacki, who hammered Russian Maria Kirilenko 6-0 6-3, and fourth seed Elena Dementieva of Russia, who eased past Kirsten Flipkens of Belgium 6-4 6-2.
Zheng, a surprise semi-finalist at the Australian Open in January, broke Sharapova three times in the final set before clinching victory in a little under three hours with a searing forehand winner that clipped the baseline.
The 26-year-old Chinese, seeded 18th, punched her right fist in delight after booking a place in the fourth round against Australian wildcard Alicia Molik, a 6-0 6-2 winner over British qualifier Elena Baltacha.
"It was a tough match," a smiling Zheng told reporters. "It was good fighting in the final set. I was 2-3 down and I come back to 6-3. It's not easy and I'm so tired.
"She played so hard... but I tried to serve to her body more, because she has long arms. If I serve too wide, it's easy (for her) to hit winner. My serve always go to her body."
Zheng broke the former world number one three times to win the opening set but the 2006 champion followed suit in a protracted second set that lasted one hour eight minutes to level the match.
Early service breaks were traded in the third before Sharapova appeared to take control when she again broke the Chinese, forcing a baseline error by her opponent with a powerful forehand to lead 3-1.
After taking a medical timeout for treatment on her right elbow, Sharapova was then broken in her next two service games and Zheng, a feisty counter-puncher, took advantage by holding her own serve to close out the match.
Sharapova, who had clinched her 21st WTA title in Memphis last month, piled up 62 unforced errors in the third-round encounter compared to 40 by Zheng.
"I'd have periods of good games, and then the problem is trying to keep them all together and not be so up-and-down," the 22-year-old Russian said. "It was just very inconsistent.
"She's like a ball machine. She hits a lot of balls back, hits them hard and deep. I should have done a much better job on her serve because that is definitely one of her weaker parts of the game."
Asked how much her problem elbow affected her in the final set, Sharapova replied: "Not in my game, but on my serve it was really blocked extending it.
"I just felt like I couldn't really extend it all the way. It was a little stuck. I'm sure I'll have a check-up on it."
Earlier, fifth seed Agnieszka Radwanska of Poland swept aside 31st-seeded Argentine Gisela Dulko 6-1 6-0 and 11th seeded Frenchwoman Marion Bartoli crushed American Jill Craybas 6-2 6-0. (Editing by John O'Brien; To query or comment on this story email firstname.lastname@example.org)