Zheng Jie(L) and Yan Zi of China celebrates after they battled into the quarter finals of the Australian Open with victory over Elena Dementieva and Flavia Pennetta Jan 23,2007.[Xinhua]

Defending doubles champions Zheng Jie and Yan Zi battled into the quarter finals of the Australian Open with a hard fought 4-6 6-1 6-2 victory over Elena Dementieva and Flavia Pennetta on Tuesday.

The number two seeds, who were also successful at Wimbledon in 2006, had enjoyed a relatively easy progress to the third round after dropping just three games during comfortable straight sets victories but were handed an early scare at the Margaret Court Arena.

Dementieva and Pennetta, who created 11 break points in the first set, converted the crucial break midway through the first after each pair had shared early breakthroughs on their opponents serve.

But the Chinese duo responded and raced through the second set in 38 minutes and grabbed an early break in the third as the match looked to have turned in their favour.

But Dementieva and Pennetta, the 14th seeds, responded with a break of their own to level at 2-2 before the defending champions finally found the breakthrough and opened up match winning a 4-2 advantage.

Zheng and Yan will face compatriots Sun Shengnan and Sun Tiantian in the last eight.