"It was nice to see the offense come alive," manager Matt Williams said. "We did it early."
Rendon opened the scoring in the first inning when he sent a double to right-center field off of starter Dallas Keuchel, scoring center fielder Denard Span, who reached base on an infield single that ended his hitless streak at 0-for-18.
Later that inning, after a walk to first baseman Adam LaRoche, Zimmerman connected on his first RBI extra-base hit of the night to give the Nationals a 2-0 lead.
Zimmerman added to the lead against Keuchel -- who surrendered four earned runs on six hits over five innings -- in the third inning with his second RBI double in as many at-bats. Shortstop Ian Desmond then singled to left field to extend Washington's lead to 4-0.
"He's a good pitcher," Zimmerman said of Keuchel, who entered Tuesday's contest with a 2.38 ERA. "You've got to make him get the ball up. He's got a lot of movement. He's been really good this year. We did a good job of getting some pitches we could drive with runners in scoring position."
Nationals starter Tanner Roark struggled with the command on his two-seam fastball on Tuesday night but battled through humid conditions to earn the win. He surrendered just one earned run on seven hits over five innings despite encountering a bases-loaded jam with no outs in the top of the fourth.
"It was a grind all game," Roark said. "Just one of those days. I couldn't get ahead but came up with big pitches, and of course, we come out early and scored runs. It takes a lot of weight off."
Roark typically relies on his fastball command to get ahead in counts and pitch to contact. Tuesday night, though, the right-hander had to resort to his off-speed pitches early in at-bats for strikes when he realized his two-seamer was not running back over the plate.
"My bailout was my curveball tonight," Roark said. "Thank God that was there."
Washington turned to the bats again in the sixth inning, when Rendon blasted a two-run double into the left-field corner to extend the lead to five runs.
"Keep it short and simple is what I try and do," said Rendon, who finished 2-for-4 with three RBIs. "And it happened to work tonight."
Reliever Drew Storen pitched a scoreless seventh inning before the Astros scored four against Clippard, who had not surrendered an earned run in 22 2/3 innings entering Tuesday.
Three straight hits off Clippard to start the inning brought home Houston's second run before an RBI bloop single from center fielder Dexter Fowler and a two-run rocket double from second baseman Jose Altuve cut the Nationals' lead to 6-5. Williams pulled Clippard with two outs, and right-hander Aaron Barrett forced right fielder George Springer into a lineout to end the inning.
"Great job of battling," Astros manager Bo Porter said. "That's a really good bullpen they have over there."
The Astros' late push fell one run short, though, as Nationals closer Rafael Soriano pitched a scoreless ninth to earn his 14th save. It marked Washington's first victory since last Wednesday.
And two days after the Nationals closed out their trip with the same stagnant offense that plagued the first two months of their season, the bats returned to form and provided runs early and often.
"I wish we were going to score six runs every game," Zimmerman said. "I can tell you right now, we're going to have three or four more games a couple more times this year where we score one or two runs. It's unfortunate, but it happens. We've just got to keep doing what we've been doing all year, and trust that it will come around."