Indian tennis star Sania Mirza and her Swiss partner Martina Hingis survived a scare before pulling off a three-set win over the Chinese pair of Yi-Fan Xu and Saisai Zheng in the WTA Qatar Open to extend their unbeaten streak to 41 matches in Doha today.The top seeded Indo-Swiss pair toiled for one hour and 24 minutes to prevail 6-4, 4-6, 10-4 over the unseeded Chinese duo to enter the quarterfinals. They got a bye in the first round in the hard court tournament.Sania and Hingis have together won four titles this year out of an overall trophy count of 13.