The second-seeded German crushed Australian Jordan Thompson 6-1, 6-1 to move ahead after successfully overcoming the challenging switch from Paris Olympic clay to fast North American hardcourt.
The 2017 champion in Canada took a victory as fellow seeds Daniil Medvedev, Stefanos Tsitsipas and Tommy Paul all lost in the second round.
Zverev, a Paris quarter-finalist, was pleased to be the exception to the rule as he won his tour-leading 48th match of the season.
"You only have two or three practice sessions plus it's a six-hour time difference," he said.
"It's extremely difficult to go straight from clay to cement -- you just cannot compare the conditions. Also, the balls here are tricky and hard to control.
"I'm happy to be through, but it's not easy to play a Masters straightaway. That's why there have been some exits from the top guys."
Medvedev was frustrated in his quest for a first title this dry-spell season, with the third seed overwhelmed as Alejandro Davidovich Fokina made a reset after losing the second set to earn a 6-4, 1-6, 6-2 win.
The Spaniard had lost four previous matches against a player whose last title came in Rome 15 months ago.
"It was not easy for me," the 42nd-ranked winner said. "It has not been an easy year for me.
"But to beat a player like Daniil gives me a lot of strength and power to continue. I'm very happy for this win.
"After losing the second set, I returned to my tactics of the first set. I tried to stay calm and not think about the result."
Nishikori advances
Former world number four Kei Nishikori advanced to a Masters third round for the first time in three years with a 6-4, 6-4 defeat of eighth seed Tsitsipas that took just 78 minutes.
Japan's former US Open finalist, who has had several seasons of hip injury drama, is playing with a protected ranking of 576, but making comeback progress this week.
Nishikori (2016) and Tsitsipas (2018) have both played Canadian finals, with the Asian earning his first top-20 match win since 2021.
"It was a great win for me. It means a lot to beat Stef," Nishikori said. "I was playing really well, I stayed aggressive and didn't miss too many balls."
Nishikori built up a 5-2 lead in the opening set but came under threat as his Greek opponent spun off 10 straight winning points to pull to 4-5.
Nishikori claimed the set and broke once more to secure the win on his first match point.
"I was really nervous and ready for 5-all," the winner said. "But this is tennis and a lot can change.
"Somehow I managed to hold, then stayed calm. I feel like I'm on the right track."
Fifth seed Andrey Rublev matched his Canadian career-best with a third round spot after defeating Tomas Martin Etcheverry 7-6 (7/3), 6-2.
He will next face Brandon Nakashima, who put out 10th-seeded Olympic double medalist Paul 6-2, 6-7 (5/7), 6-1 with nine aces and five breaks of serve.
Rublev, who has notoriously melted down several times during 2024 matches, kept his cool in victory.
"I'm proud I was able to stay calm. I was not playing well at the start and he was very aggressive, he was running for every ball," he said.
"I had stress inside but was able to stay calm and compete. In the end I was able to turn around the match."
Grigor Dimitrov, a semi-finalist here a decade ago, lost just one game as he beat qualifier Rinky Hijikata of Australia.
