The Cubs, meanwhile, faced a short bus ride. Plenty of their faithful followed them up I-94, once again turning the Brewers' ballpark into "Wrigley North."
This was baseball's first neutral-site no-hitter, the Elias Sports Bureau said.
"It was a long travel day and Hurricane Ike," Astros manager Cecil Cooper said. "That's what I put it on. That and having two days off. I'm not saying he wasn't good."
Zambrano, known for his emotional displays on the mound, kept himself in control until striking out Darin Erstad to finish off the gem.
Zambrano (14-5) dropped to his knees and pointed to the sky with both hands after getting Erstad to swing and miss for his season-high 10th strikeout. The big righthander was mobbed on the mound by his teammates.
"I'm a little confused right now," the three-time All-Star said. "I still can't believe it. It's a great feeling, a feeling that you can't describe."
Zambrano walked one and hit a batter in the Cubs' first no-hitter since Milt Pappas's against San Diego in 1972. This was the 13th no-hitter in team history, including five in the late 1800s.
This was the second no-hitter in the majors this season - the Red Sox' Jon Lester did it against Kansas City May 19.
The Astros only once came close to a hit. David Newhan lined a drive that first baseman Derrek Lee jumped to catch to end the fifth inning.
While the Astros batted last, Cooper wasn't happy with the arrangement.
"This is not a home game. This is definitely an advantage for the Cubs and that's saying it as mildly as possible," he said.
Zambrano began the ninth by getting Humberto Quintero to ground out on one pitch, his 100th of the game. After pinch hitter Jose Castillo also grounded out, Erstad chased a full-count pitch low and away.
Manager Lou Piniella planned to limit the 27-year-old Venezuelan ace to 100 pitches in his return to the rotation. Having recently had an anti-inflammatory shot, Zambrano managed to come close - he threw 110 pitches, 73 for strikes.
"What can I do?" Piniella said. "I was even hesitant to warm someone up."
The Cubs took a 7 1/2-game lead in the NL Central over the fading Brewers, who were swept in a doubleheader at Philadelphia.
