The Nationals swept the four-game set from the Astros with three one-run victories -- two in extra innings -- and Thursday's five-run victory.
Brett Wallace, who finished 3-for-4, doubling and striking out against Zimmermann, was impressed with how the young righty mixed his pitches.
"He can throw everything in every count, really," Wallace said. "To me, that's what stuck out the most. He's in the zone a lot. He's not one of those guys that's tiptoeing around guys or out of the zone."
Astros hitters other than Wallace went 2-for-27, scratching both hits off Zimmermann. The right-hander lowered his ERA to 2.35 with six shutout innings.
"It was tough battling," Houston manager Brad Mills said. "He's got a [2.35] ERA for a reason and I think we saw that tonight."
Astros starter Lucas Harrell went five innings, allowing two runs on five hits and two walks. At home, Harrell is 6-2 with a 2.14 ERA.
Harrell breezed through the first three innings, striking out five and allowing just a one-out single to Roger Bernadina in the first.
"That was the best I've felt in probably my past four or five starts," Harrell said.
The right-hander ran into trouble in the fourth, putting runners on first and second with no outs. Adam LaRoche's RBI single scored Bernadina from second and Michael Morse's sacrifice fly scored Ryan Zimmerman from third, giving the Nationals a two-run lead.
Harrell needed 32 pitches to escape the fourth with the bases loaded.
After getting a double play for the first two outs of the fifth, Zimmerman grounded out on Harrell's 100th pitch to end the inning. Brandon Barnes pinch-hit for Harrell in the fifth and struck out.
"I definitely felt like I had more in the tank," Harrell said. "I felt like that fifth inning, I kind of got back to my strengths. I had a fairly quick inning."
Harrell threw 112 pitches in his last start, prompting Mills to be cautious with the team's best pitcher in recent weeks.
"The last thing I want to do is get him hurt," Mills said.
Mills said he thought Harrell, a "max-effort individual," expended a lot of energy trying to get out of the fourth.
"When that type of guy starts struggling a little bit, he continues to try to work himself out of it," Mills said. "That max effort gets him those high pitch counts and he blows off a lot of steam. He ran out of gas, really, in that fourth inning."
Morse hit a towering shot to left field off reliever Mickey Storey in the sixth to push Washington's lead to 3-0. In the eighth, Morse hit another solo homer, this time to right field, off reliever Fernando Rodriguez.
Washington added another run in the ninth on Zimmerman's sacrifice fly.
Zimmermann was just as good as Harrell early, also striking out five and allowing one hit -- Wallace's double -- in the first three innings. The Nats' starter maintained that dominance for most of the game, though.
Zimmermann threw 87 pitches, 57 for strikes. Every Astro who faced him struck out at least once. Justin Maxwell whiffed twice, giving Zimmermann 11 strikeouts, tying his career high.
"He's coming at you," Wallace said. "When he gets ahead, he's got a couple pitches that he feels comfortable putting guys away with. He's a good pitcher. We caught him on a good night. We just had to battle as much as we could."
Since Wallace returned to the Astros on July 30, he's batting .294. He has seven multi-hit games in the Majors this season.
Nationals manager Davey Johnson said that the people calling his team "flat" in this series don't understand that the Astros don't just lay down.
"This is a good little team," Johnson said. "They've got some good little players and they've got some good pitchers. I liked Harrell. They battle you. They don't make a lot of mistakes out there."