Ethier is one of only three players in baseball history with hits in 21 or more consecutive games in April. Ethier's former manager Joe Torre had a 22-game streak in 1972 and the Arizona Diamondbacks' Danny Bautista hit in 21 straight in 2004.
"It's about going up there and executing and being confident," Ethier said. "It's nice knowing I don't have to do too much with guys in front of me and behind me doing their jobs and picking me up. It makes my job a lot easier."
Aaron Miles led off the game with a triple into the right-field corner to set up the easy RBI opportunity for Ethier, who finished with two hits.
"We saw yesterday that that team fights back so we jumped on them early and tried to stay on them," said Miles, who had three hits.
The Dodgers, who have won four of five, tagged Zambrano with his first loss since June 25.
"I knew sooner or later I was going to lose a game, unfortunately it was today," Zambrano said. "I enjoyed the winning streak a lot, but it's over with. Let's get another win on my next time and I'll be ready for that."
Zambrano (2-1) settled after a rocky opening and gave up only one more run through five innings of work.
Zambrano won eight straight from Aug. 14 through the end of the 2010 season -- he was suspended after a June 25 dugout tirade and didn't return until late July. And he was 2-0 through four starts entering Sunday's game. The streak was the Cubs' longest since Rick Sutcliffe won 16 straight between 1984-85.
"I was a little off today," said Zambrano, who gave up eight hits and struck out four. "Pitching in the first inning wasn't good. My sinker was not good, but other than that I was able to throw five innings."
Cubs manager Mike Quade could tell Zambrano wasn't sharp.
"He just didn't make quality pitches from what I can see," he said. "He's been pretty good and it's just unfortunate that he had a rough first inning today."
Dodgers right-hander Hiroki Kuroda (3-2) gave up three hits and two first-inning runs but then settled down and scattered six hits the rest of the way. He surrendered three runs -- two earned -- struck out seven and walked none.
"I had really good movement on the splitter today," Kuroda said through an interpreter. "With five runs of support, I felt responsible for winning this game."
Miles led a succession of first-inning base runners when he opened with a triple down the right field line. No. 2 batter Casey Blake was hit by a Zambrano pitch and Ethier followed with an infield single that scored Miles.
Matt Kemp drove home Blake with an infield single while Jerry Sands' double scored Ethier. James Loney hit into a fielder's choice that brought home Kemp, while Sands closed the scoring on a Rod Barajas sacrifice fly.
The Cubs scored twice in the bottom of the first while Kuroda struck out three.
After seeing seven runs scored in the first, Dodgers manager Don Mattingly had felt he might be in for another wild ride, similar to the 10-8 loss just a day earlier.
"When they get the two [runs] right back, you kind of feel like you have a chance to get into one of those games," Mattingly said. "Both guys really settled in and pitched well after that."
The Dodgers added a solo run in the third when Kemp doubled with one out and came home on Loney's two-out single to left.
In the sixth, Barajas singled and scored off left-handed reliever John Grabow. Miles' single to left brought Barajas home for a 7-2 Dodger lead.
Dodgers infielder Juan Uribe missed his second straight game with a sore thigh. He was hitting .435 (10-for-23) with two homers, nine RBI and five runs scored during a recent six-game hitting streak ... Castro was hitting .500 in 46 at-bats when leading off entering Sunday's series finale, including four hits on Saturday. He moved down to third on Sunday with Kosuke Fukudome leading off ... The Cubs host their first official night night game Monday against the Colorado Rockies. ... Exactly 49 years ago, Dodgers lefty Sandy Koufax tied his own team record by striking out 18 Cubs at Wrigley Field in a 10-2 victory. ... The Cubs and New York Yankees are the only teams in baseball with winning or losing streaks no longer than two games ... Fukudome is off to his best March/April big league start with a .417 average entering Sunday. He has a .346 career average (93-for-269) in March/April games through four seasons.