Paes and his Czech partner, seeded fourth, had to battle for two hours and 12 minutes to overcome 14th seeded veteran French pair of Michael Llodra and Nicolas Mahut 7-5 4-6 6-3.
Up next for Paes and Stepanek could be India's Divij Sharan and his Taipei partner Yen-Hsun Lu. The duo defeated the Israeli team of Jonathan Erlich and Andy Ram 6-4 5-7 7-6 (2) in a hard-fought contest.
Sania and China's Zheng, seeded 10th, took out sixth seeds Anna-Lena Groenefeld of Germany and Kveta Peschke of Czech Republic 6-2 6-3 in one hour and 12 minutes.
Sania and Zheng never faced a break points in the match and broke their rivals twice in each set to move to the last- eight pairs stage.
In the Paes-Stepanek match, after trading breaks, the opening set was on serve till the 11th game. The Indo-Czech pair had its first set point in the next game but Stepanek hit a forehand to net.