Nearing the end of a dismal season, the Nationals continued a six-game winning streak in the third game of the four-game series.
With the score tied 2-2, Guzman doubled to right in the 10th, scoring Zimmerman and Adam Dunn.
Atlanta answered with two runs in the bottom of the inning. Pinch-hitter Kelly Johnson doubled to center, scoring Adam LaRoche, and Greg Norton, also pinch-hitting, singled to center, scoring Johnson.
Maxwell's two-out, two-run homer to right came in the top of the 11th off losing pitcher Manny Acosta (1-1).
Zack Segovia (1-0) gave up a walk, then shut down the Braves in the 11th to get the win.
Swim Week Miami Beach 2014 [PHOTOS]