Pettersson tied it 1-1 at 4:03, diving with one hand on his stick to sweep in his own rebound after Fleury slid across to stop his first attempt from the bottom of the left face-off circle.
Zykov scored on a rebound during a power play to make it 2-1 at 9:51 of the first period.
"It was great to get everybody going and to see a guy like [Zykov] get his first goal," Marchessault said.
Vegas outshot Vancouver 19-5 in the second period and scored twice.
"We got beat to every puck in the second period," Green said. "When that happens, you are going to spend a lot of time in your zone."
Marchessault finished a cross-ice backhand pass from Reilly Smith to make 3-1 at 4:46, and Stone finished a partial break at 9:16 with a wrist shot over Markstrom's glove to make it 4-1.
Marchessault, who wasn't drafted in the NHL, scored eight goals over his first three seasons and 49 games with the Columbus Blue Jackets and Tampa Bay Lightning. He has 62 goals in 195 games with the Golden Knights after scoring 30 with the Florida Panthers in 2016-17.
"Better when it's during a win also," he said of the milestone. "Honestly it's been kind of a roller coaster career, and it's fun to get a bit more stability in Vegas. It's been good."
Boeser made it 4-2 at 5:02 of the third, and Virtanen scored on a power-play rush at 17:24 to make it 5-3.
