Cleanup hitter Mark Reynolds, though, rolled over on a pitch and the Cubs turned a 6-4-3 double play to end the inning.
"For a guy like that, that's when you have to get to him," D-backs manager Bob Melvin said of Zambrano. "If you can get to him early and get him out of whack a little bit and we did have a couple of opportunities and couldn't take advantage of them."
"He executed his pitch there well and we definitely needed that," Cubs catcher Koyie Hill said. "There was definitely a momentum swing there because after that Zambrano found his rhythm."
Petit played with fire in the first two innings as he gave up three fly balls that were caught on the warning track. One of those was by Alfonso Soriano to lead off the game and when he came up for a second time Soriano didn't come up just short. Instead, his ball found the left-field seats for a three-run homer.
The D-backs, though, had a chance to respond in the bottom of the third, but with two out and two on, Chad Tracy grounded into a fielder's choice to end the threat.
"We didn't cash them in early, I didn't cash one in," Tracy said. "He made his pitches when he had to."
That's something that could not be said of Petit, who was chased during a four-run rally by the Cubs in the fourth that included a two-run homer by Mike Fontenot.
"Early on, first couple of innings he looked pretty good, then he just couldn't stop the bleeding when they got going on him a little bit," Melvin said of Petit, who is filling in for the injured Brandon Webb. "Got himself into some bad counts and had to throw some balls over the middle of the plate and they made him pay."
Suddenly, the Cubs were up 7-0 and Zambrano seemed to be rolling.
"They just kind of took it out of us," Tracy said. "They swung the bats well and kept adding on."
Indeed, the Cubs scored two more in the fifth and one each in the sixth and seventh innings the final run coming on a homer by Zambrano himself, his first of the year and 17th of his career.
"He got comfortable; he had a nice lead to work with," outfielder Chris Young said. "I don't know if even necessarily had his best stuff today. He got a little erratic at times. He was all around the zone. When he needed to lock it down he did a good job at it so, overall, he pitched a good game. "
The D-backs were feeling pretty good about themselves heading into the game. They had finally managed to string together two wins and looked impressive doing so Monday when they stole five bases in beating the Cubs.
Now, they are left with trying to salvage the series by winning the finale Wednesday afternoon.
"We can still win the series tomorrow and it will be a good series," Young said. "We're playing good baseball. We battled offensively. We got 10 hits, put a few runs on the board, just couldn't put that big inning together, but I don't think we took a step back in any way. I still feel like we have tomorrow to win and we can still get out of town winning the last two series at home."