The right-hander pitched two innings in his Cactus League debut Friday, allowing two hits in Chicago's 8-6 loss to a San Francisco Giants split squad.
"I feel better about everything. I feel better than last year," Zambrano said. "At this point, I was 75-80 percent. Now I'm 90 percent. That's good. When I feel like this, I'm ready to go to the season."
Zambrano came to camp last year admittedly distracted by contract talks. He avoided salary arbitration, but it wasn't until August that he and the Cubs agreed to a $91.5 million, five-year extension that kept him off the free-agent market.
Despite the uncertainty that seemed to bother him at times, Zambrano finished 18-13 with a 3.95 ERA.
On Friday, he gave up an unearned run that resulted from his fielding error in the first inning, when he couldn't come up with Eugenio Velez's bunt.
"I was too rushed. I should have been more patient and calm," Zambrano said.
Velez stole second and scored on a single by Brett Harper, putting the Giants up 1-0.
The Cubs, who beat San Francisco in Thursday's Cactus League opener for both clubs, scored three times in the bottom of the first against Jonathan Sanchez, who walked Alfonso Soriano and Kosuke Fukudome. Mike Fontenot drove in a run with a ground-rule double.
Cubs lefty Rich Hill gave up a run in the third on a sacrifice fly by Harper.
"I thought Zambrano worked well. I thought Hill worked well," Cubs manager Lou Piniella said.
The Giants came from behind twice. Minor leaguer Ryan Rohlinger hit an eighth-inning grand slam off non-roster lefty Les Walrond to rally San Francisco from a 6-4 deficit.
Sanchez worked one inning, allowing three hits and three runs. Vinny Chulk got the win with one inning of work. He gave up two hits and a run.
The Giants kept most of their regulars in Scottsdale, where they lost 5-3 to Seattle.
Cubs 3B Aramis Ramirez has missed both Cactus League games with a "tight" right shoulder. He is day-to-day. Ramirez took grounders at third base but didn't throw. He also took full batting practice. "I'm just a little tender in the shoulder, no reason to push it," Ramirez said. "I'll take a couple of days and see how it goes."