Zaun hit a solo homer in the second inning, Reimold hit a three-run shot in the fifth and Huff hit a solo homer in the seventh. Huff and Adam Jones had two hits apiece for the Orioles, who can complete a three-game sweep with a win Sunday.
Winner Jeremy Guthrie (6-7) gave up three earned runs and five hits in five innings.
Closer George Sherrill, the last of five Baltimore pitchers, earned his 16th save with a 1-2-3 ninth.
Adam Dunn, Josh Bard and Austin Kearns each drove in a run for Washington. Josh Willingham and Cristian Guzman had two hits each for the Nationals, who have lost five of six.
Losing pitcher Shairon Martis (5-3) gave up four earned runs and six hits in five innings in his third straight loss.