Hsieh and Peng followed up their Wimbledon title with another title in Cincinnati and though they lost their opener in New Haven, they have returned to their recent great form at Flushing Meadows and have now won 13 of their past 14 matches.
The key stat in fourth-seeded Hsieh and Peng's 64 62 defeat of 15th-seeded Jelena Jankovic and Mirjana Lucic-Baroni was second serve conversion rate, with Hsieh and Peng winning 14 out of 20 and Jankovic and Lucic-Baroni winning just nine of 28. Next up for the Taiwanese-Chinese duo are 10th-seeded Sania Mirza and Zheng Jie.
No.1 seeds Sara Errani and Roberta Vinci joined Hsieh and Peng in the quarterfinals with a 61 75 triumph over No.16 seeds Anabel Medina Garrigues and Flavia Pennetta, converting on seven of nine break point chances in the process. Dating back to the third round of last year's US Open, the defending champions have now won 13 straight sets here and are 13-2 all-time at this event. Three more wins and the Italians will became the first repeat champions here since Virginia Ruano Pascual and Paola Suárez won three US Opens in a row from 2002 to 2004.
Second-seeded Russians Ekaterina Makarova and Elena Vesnina had the toughest win of the day, but managed a 57 62 64 defeat of 13th-seeded Cara Black and Marina Erakovic in two hours and 25 minutes. It was their 11th win in their last 12 Grand Slam matches and set up a quarterfinal with eighth-seeded Ashleigh Barty and Casey Dellacqua.