"We can hit," Nationals interim manager Jim Riggleman said. "We're more surprised when we don't score some runs than when we do score them."
"Anytime the starting pitcher gets into the seventh and we can score that many runs, I'll take our chances that we're going to have a pretty good day," Zimmerman said.
Alcides Escobar hit his first major league homer for the Brewers, who had won two straight, but his error helped Washington score three unearned runs off Manny Parra in the first. Nyjer Morgan reached on an infield single and was safe at second when the shortstop couldn't handle Parra's throw to second on Guzman's bouncer to the mound.
"The ball, when Manny throw, I'm waiting for it on my side," Escobar said. "He throw easy, and I see the runner very close to me. I try to jump and I drop the ball."
Zimmerman then delivered a run-scoring single to center and Belliard later added a two-out, two-run bloop hit to right.
Morgan's successful suicide squeeze plated Mike Morse and Guzman's two-out solo shot to left made it 5-0 in the second.
"You're always trying not to give up any hits -- that's the goal always -- but it's a little bit of extra comfort in the back of your mind that if you do make a mistake, you're still right there," Stammen said. "You don't have to be picture perfect."
Parra, who had won four of his past five starts, allowed eight runs -- five earned -- and eight hits over 3 1/3 innings.
Dunn connected for his 33rd homer in the third, hitting a leadoff drive into the second deck in right. Guzman singled with one out in the fourth before Zimmerman launched his career-high 26th home run to center, knocking Parra (8-10) from the game.
Escobar lined Stammen's 2-1 pitch into the left-field stands in the fifth to cut the Nationals' lead to 8-2. But the slick-fielding rookie's miscue still stood out.
"That's nice that he hit a home run [but] I'm looking for him to be a Hoover out there in the field," Brewers manager Ken Macha said. "This guy's supposed to be an impact glove man."
Milwaukee's Ryan Braun was ejected for throwing his helmet in the sixth after shortstop Guzman ranged into short left field to snag his grounder and throw him out at first for the inning's first out. Braun used two hands to heave his headgear in disgust and got tossed by first base umpire Mike Muchlinksi.
Nationals LHP Sean Burnett bruised his left thumb trying to field Mike Cameron's grounder in the seventh. Riggleman said he might be unavailable for a couple of days. ... For the fourth time this season, Macha batted his starting pitcher eighth, with Escobar hitting ninth. ... Washington OF Elijah Dukes was scratched with a sore, blistered left thumb. He was replaced by Morse in right field. ... The three homers allowed by Parra were a season high. ... Washington's Josh Willingham was hit by a Carlos Villanueva pitch in the sixth, the team-high 12th time this year he's been plunked.