American sixth seed Riske eased past Chinese Zheng, claiming a routine 6-0 6-1 win at the Tianjin International Tennis Center.
Riske - a six-time winner on the ITF Tour but without victory on the WTA circuit - wrapped up proceedings in a little over an hour as she qualified for the decider in the inaugural edition of the Tianjin Open.
The 24-year-old was far too strong throughout the final-four encounter, taking the opening set after claiming three of five break points on offer.
Zheng went a little better in the second set and managed to hold serve as she finally got on the board to avoid a dreaded double-bagel.
Riske will now go head-to-head with Swiss teenage sensation Belinda Bencic, who benefited from an early retirement.
Bencic - the third seed - was up 3-1 after 18 minutes in the first set before China's second seed Peng Shuai retired.
The 17-year-old - a quarter-finalist against Peng at the US Open last month - will contest her first WTA Tour final.