Joe Saunders (5-8) couldn't make it through the third inning, yielding eight runs, five earned, on nine hits and two walks in 2 2/3 innings. With 11 earned runs allowed in his past 8 1/3 innings, he has watched his ERA soar, from 4.35 to 5.07.
"I thought I had great stuff," Saunders said. "I got ground balls. Today was one of those days where you make the pitches and they still find holes. [You have to] forget about it and move on."
The Angels avoided a shutout thanks to Torii Hunter's two-out RBI double off Zambrano (3-5) in the fourth following Kevin Frandsen's single and steal. By then the score was 8-0 and Saunders was in the clubhouse, showered and shaved.
"I was able to command both sides of the plate with lefties and righties," Zambrano said. "One thing I know is when I have my good sinker, I know it's tough to hit that pitch. Thank God everything went good today and we avoided a sweep."
Angels manager Mike Scioscia was impressed with Zambrano.
"He got in that zone and knew what he had to do with that lead," Scioscia said. "We let things get out of hand with some of the plays we didn't make in the field.
"Obviously, it was a tough start for Joe. If we made a couple of plays, it would have let him stay in the game. Those guys did a good job in the batter's box and beat us pretty bad."
The Cubs scored twice in the first inning, a throwing error by second baseman Howard Kendrick on Alfonso Soriano's infield hit making one of the runs unearned after two singles had rolled through the left side.
Jeff Baker's RBI double and Lee's sacrifice fly made it 4-0 in the second inning after shortstop Brandon Wood was unable to get an out at third on Marlon Byrd's one-out roller.
"I thought we had him over there," said Wood, playing his fourth straight game at shortstop with Erick Aybar nursing an injured left knee. "Looking back on it, you'd want to take the safe play and go to first."
After Geovany Soto led off the third with his eighth homer of the season, the Cubs produced three more runs, two coming on Lee's double after an error by Wood on Baker's grounder that made two of the runs unearned.
"I backed up on it, and it had topspin on it and came up on me," the normally sure-handed Wood said. "I didn't anticipate it coming up that high.
"Erick's one of the best shortstops in the game. It's not like I'm going to come in and fill those shoes. I can only do what I'm capable of doing. Today the ball just ate me up a little bit."
The Angels were returning a favor with their generosity, the Cubs having handed them four unearned runs in each of the first two games.
"We won the series," Kendrick said. "Things didn't go well today, but we'll take that."
The Angels headed west after the game to begin their longest homestand of the season, 12 games, starting with a three-game set with the Dodgers that kicks off on Tuesday night.
Having won 13 of their past 18, the Angels are 7-5 in Interleague Play.
Young right-hander Sean O'Sullivan was effective in relief of Saunders, allowing one run on three hits in 3 1/3 innings.
The colorful Zambrano, arguably the game's best hitting pitcher, was 2-for-4 with a run scored and an RBI. He went seven innings, yielding eight hits and a walk while striking out seven.
"He looked like his old self," Kendrick said. "He was moving it in and out, with good stuff. He made some mistakes, and we missed them. He made pitches when he needed them."
A slugger in his youth in San Diego, O'Sullivan had one of the Angels' best at-bats against Zambrano. After taking a slugger's cut and missing, he worked the count full before grounding out sharply to second to end the fifth.
Closer Brian Fuentes faltered in his first appearance in a week. He recorded only two outs in the eighth inning, when the Cubs reached him for three earned runs on four hits and a walk. Fuentes' ERA soared, to 6.23, as he continues to search for consistent command.
"Brian looked like the ball was coming out of his hand fine," Scioscia said. "He missed a couple spots, and those guys squared up some balls."
Trevor Bell left runners in scoring position in relief of Fuentes when he blew away Baker with a 96-mph heater.