SAN DIEGO (Ticker) -- Carlos Zambrano cannot be overlooked much longer.

Zambrano allowed one run in six innings to win his fourth straight start and Sammy Sosa and Moises Alou hit back-to-back homers as the Chicago Cubs rolled to a 9-3 victory over the San Diego Padres .

On a pitching staff that features All-Stars Kerry Wood and Mark Prior , Zambrano has gotten little attention during a breakout season. He joined Wood as the only pitcher on the team with double-digit victories, and his 3.25 ERA trails only Prior for the best by a Cubs' starter.

"They all have good command, but Zambrano has the best movement," San Diego manager Bruce Bochy said. "That's a nice staff they have assembled. When you throw three guys like that, it's really a pretty good threesome."

Zambrano (10-8) yielded just seven singles and three walks while matching a season high with eight strikeouts. He threw 79 of 119 pitches for strikes.

"I'm glad Zambrano got the victory," Cubs manager Dusty Baker said. "He threw a lot of pitches, but he made the pitches when necessary. They left a lot of guys out there and Zambrano got out of it."

The Cubs had a 1-0 lead with two outs in the third when Sosa belted a two-run homer off Padres starter Kevin Jarvis . It was Sosa's 16th homer of the season and 525th of his career.

Alou followed with his 17th homer for a 4-0 cushion and Eric Karros added a two-run shot off reliever Joe Roa in the fifth.

Jarvis (4-4) was shelled for seven runs and nine hits in just 3 2/3 innings. The Cubs scored all seven runs off him with two outs.

"Kevin has been throwing very well, but today he just struggled," Bochy said. "It seemed like every time they scored, he was an out away from getting out of the inning. He wasn't on top of his game. We were facing a good pitcher and we just got too far down."

Chicago extended its winning streak to four games and swept a three-game series in San Diego for the first time since June 28-30, 1993.

Zambrano worked out of a bases-loaded jam in the third inning and cruised until the sixth. He allowed an RBI single to Ryan Klesko and loaded the bases before avoiding further damage.

The Cubs jumped on Jarvis early as Kenny Lofton opened the game with a single, stole second and scored on a double by Alou three batters later.

Jarvis retired the next six hitters before Ramon Martinez singled with two outs in the third. Sosa followed with his fifth career homer off Jarvis, driving a 1-2 pitch over the left field wall.

Alou hit his homer the opposite way over the right field fence on a 1-1 pitch.

Lofton made it 5-0 with a run-scoring single in the fourth and Martinez followed with a two-run base hit to stretch the lead and chase Jarvis.

Aramis Ramirez started the fifth with a single and Karros - a San Diego native - followed with his 10th homer to give Chicago a nine-run advantage.