Sabalenka beat Zheng to pick up her second Australian Open title earlier this year and used the same playbook at Arthur Ashe Stadium, where she dominated the seventh seed with her trademark mighty forehand.
Fresh off winning the Olympic title, Zheng appeared drained and was missing one of the best weapons in her arsenal as she only made 44% of her first serves.
"She's such an aggressive player," Sabalenka said. "She's playing such incredible tennis and it was very tough facing her."
Sabalenka got a head start when Zheng dropped her serve with an unforced backhand error in the second game and the second seed went up another break when Zheng sent a forehand into the net in the sixth game.
Sabalenka kept the pressure up in the second set, where she put up just six unforced errors, and Zheng dropped her serve in the first and fifth games after costly backhand mistakes.
The Belarusian produced a fine backhand winner at the net on the penultimate point and she clinched it with an unreturnable serve.
Sabalenka will next play American Emma Navarro.
She beat the 13th seed Navarro in the fourth round at Roland Garros but lost to her on the hard courts at Indian Wells earlier this year and told fans she expects a tough fight.
"She's a great player," said Sabalenka. "I saw her matches here, she's playing incredible tennis and yeah it's going to be great battle and I'm really looking forward to facing her again."
