He homered twice and the Nats won their third straight game, beating the Florida Marlins 7-1 on Friday night.
"It's nice to come back and contribute and help win," Zimmerman said. "I was happy with my at-bats."
After being out since April 21 with a hamstring injury, Zimmerman connected both times on a full count against starter Ricky Nolasco.
Scott Olsen (2-1) pitched six scoreless innings, giving up five hits and striking out four. He got his first win in four starts against his former club since being acquired by Washington in November 2008.
"I'd be lying to you if I told you it didn't mean a little bit more," Olsen said. "The effect of being traded has worn off but it is nice to finally beat them. It's just nice to pitch well against people you played with and people you know."
Nolasco (2-1) gave up five runs on eight hits over a season-low four innings, while striking out seven.
"I wasn't making my pitches and they made me pay," Nolasco said. "It's going to happen. I just have to move on to my next start."
The Nationals took a 2-0 lead in the first inning on Zimmerman's two-out solo shot to left.
Zimmerman's second homer drove in Adam Kennedy, who led off the inning with a single, and made it 4-0.
It was Zimmerman's fifth career multihomer game. He finished 3-for-4, with a double and a walk.
The Marlins lost their third straight and fifth of their past six.
"It was a do-or-die play and I was really ball-hungry and in the right spot at the right time," Morgan said. "I was fired up."
If the ball had gotten by Morgan two or three runs would have scored and the Marlins would have been right back in the game.
"That was the game. The momentum had changed, they were putting a rally together," Nationals manager Jim Riggleman said. "I thought there was no way he's catching that ball. I thought it was splitting the gap. That's as good as we've seen all year."
The Nationals scored two runs in the ninth off reliever Renyel Pinto on RBI singles by Kennedy and Ivan Rodriguez. ... The Nationals' 13-10 record is the club's best mark through the first 23 games of a season. ... Olsen has beaten every NL club except the Arizona Diamondbacks. ... Marlins outfielder Cody Ross returned to the lineup after missing two games with flulike symptoms. ... Nolasco is 7-2 against the Nationals. ... They announced an attendance of 1,665 dogs for the Marlins "Bark at the Park" night.