Kuznetsova, the first Russian woman to win the US Open, is enjoying another solid build-up to Flushing Meadows having claimed her 13th career title in San Diego two weeks ago.
The World No 16 has moved into the last four in Montreal for the first time in seven visits to Canada.
Kuznetsova, seeded 11th, needed just 74 minutes to chase Zheng off centre court and improve her record against the 24th ranked Chinese to 6-0.
"I think that was one of my best matches, especially in the first set, it was amazing," Kuznetsova said. "I'm getting there but I'm not there yet. There are still some ups and downs but I am playing better."
The Russian started with a break and ended the opener the same way as she swept through the first set in 26 minutes.
The 25-year-old raced to a 3-0 lead in the second set before Zheng, the only unseeded player to reach the quarter-finals, dug in, with the players each trading a pair of breaks before Kuznetsova held serve to close out the match.
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