Upset that left fielder Matt Murton threw to second base instead of home on a fifth-inning flyout, allowing a run to score, Zambrano made a scene behind home plate, jumping up and down in disgust.
Zambrano gave up the tying run later in the inning but settled down and earned his 13th victory. Still, the tantrum was a reminder that Zambrano may have grown as a pitcher but still has to control his emotions.
Afterward, Zambrano apologized to Murton for his actions
"I think I was out of the game mentally, fighting with the umpires and some plays that happened," he said. "I apologize to my teammates. I have four years in the big leagues and I don't have to do that. I have to be calm."
The Cubs improved to 6-1 on the road trip and 69-71 for the season as Nomar Garciaparra drove in three runs. Michael Barrett hit a two-run homer and center fielder Jerry Hairston made two diving catches.
Making the bizarre night complete, a dozen or so fans dressed up in Steve Bartman costumes sat in the first couple of rows of the left-field bleachers, right behind ex-Cub Moises Alou.
With the Cubs out of the wild-card race and the Giants falling seven games behind San Diego, the only thing left to do was have a few laughs.
Beforehand, the focus was on the return of Barry Bonds, who played in a simulated game Thursday afternoon. The Giants slugger is trying to return from three right knee surgeries in time for the final three weeks of the season and may make his 2005 debut on Saturday or Sunday.
Giants manager Felipe Alou hinted he may have Bonds pinch-hit, though Bonds prefers to start in left field in his return.
"I want to play, if it's my pick," Bonds said. "But I have to do what's best for the team and I have to do what the organization and the manager choose for me to do at that moment."
Bonds will play another simulated game on Friday before conferring with doctors and general manager Brian Sabean.
"We don't know how he's going to feel waking up (Friday)," Sabean said. "We hope he's not cranky. We hope he can do the same darn thing he did today, and more. So there's a touchy-feely process that's going to go on."
Though he has denied using performance-enhancing drugs, Bonds' relationship to figures in the BALCO scandal has led to speculation that his assault on the all-time home run records have been fueled by steroid use, putting a cloud over his pursuit of Ruth and Aaron.