Zimmerman hit a long homer and Tim Redding pitched two-hit ball for six innings, sending Washington to a 5-3 victory over the Mets on Wednesday night.
"He had great command of his fastball and his curveball was very good," Nationals manager Manny Acta said. "In order to stay out there and hold those guys to one run and stay patient, it says a lot about him."
Jesus Flores hit a tiebreaking single with two outs in the seventh off Aaron Heilman, who was booed on and off the mound by the Shea Stadium crowd. Washington added three more runs in the inning, sticking Claudio Vargas with a tough-luck loss in his Mets debut.
"He did an outstanding job," New York manager Willie Randolph said. "It's just a shame we weren't able to put together any type of attack."
Brian Schneider homered and drove in two runs against his former club, but New York (20-18) dropped to a disappointing 3-3 on its seven-game homestand against last-place teams. Two of those losses have come against Washington this week.
Redding (5-3) allowed one run and struck out four, improving to 3-0 in three road starts this season. Carlos Beltran's RBI single off Jon Rauch cut it to 5-3 in the eighth, but Rauch retired Endy Chavez on an inning-ending flyout with runners at the corners.
Chavez was in the game as a replacement for left fielder Moises Alou, ejected by plate umpire Dana DeMuth for slamming his bat to the ground following a fifth-inning strikeout.
Rauch worked a perfect ninth, earning his eighth save.
"You can feel comfortable with what you're doing with each pitch, but with a lineup like that you can never get too comfortable," Redding said.
The Nationals won without cleanup hitter Nick Johnson, who traveled back to Washington for additional tests on his sore right wrist. The oft-injured Johnson strained a tendon on a swing late in Tuesday night's game and could be sidelined for a while.
Cut by Milwaukee in spring training, Vargas signed a minor league deal with the Mets and was called up Tuesday from Triple-A New Orleans. He'll get a chance to solidify a spot at the shaky back end of New York's rotation, and he looked good against Washington.
"You can't say enough. Deep into the game and he gave us a great chance to win," Schneider said.
Schneider gave the Mets a 1-0 lead in the fifth with his second homer of the year.
Zimmerman tied it in the sixth with his second home run in two nights. He drove a 2-0 delivery off the facing of the second deck of the left-field stands for No. 7 this season.
"I never like to say I got all of it, but I hit it pretty good," Zimmerman said.
Vargas (0-1) walked Elijah Dukes with one out in the seventh and was lifted for Heilman after throwing 97 pitches. Dukes moved up on a slow groundout and scored on a sharp single by Flores, the young catcher left unprotected by the Mets in the 2006 winter meeting draft (Rule 5).
Flores fought back from an 0-2 count against Heilman.
"The key at-bat of the game," Acta said. "What an at-bat for the kid that was just playing A-ball a couple of years ago. I can't say enough about that kid."
"It's frustrating when you can't hold the game where it is," Heilman said. "Not exactly smooth sailing this year."
Randolph was looking for more than one inning from Heilman because he wasn't going to use left-hander Scott Schoeneweis, who said he spent about 6-7 hours in the hospital early Wednesday with stomach pain.
"I don't feel good, but I feel better than I did this morning," Schoeneweis said after the game. "It kind of comes in waves."
Mets 2B Luis Castillo missed his third straight game with a strained left quadriceps. Damion Easley filled in again. ... Looking to get some at-bats for Dukes, Acta rested CF Lastings Milledge. Dukes was activated from the disabled list last Friday. ... After the game, the Nationals optioned RHP Chris Schroder to Triple-A Columbus to make room for RHP Jason Bergmann, who will be called up from the minors to start Thursday's series finale against New York RHP Mike Pelfrey. ... Redding improved to 13-6 against NL East teams. ... Aaron Boone started at first base for Washington and batted in Johnson's cleanup spot.