Moments after Washington's outburst ended, rains that had been falling through most of the evening intensified to the point the game had to be delayed, and eventually called.
The Nationals won for the fifth time in six contests and moved within a game of Philadelphia for the lead in the National League East.
Zimmerman hit a two-run homer in the first and a three-run shot in the fifth. He then singled in a run during Washington's big eighth inning, in which the Nationals sent a dozen men to the plate.
Cristian Guzman had a three-run double in the eighth and Josh Willingham doubled home two more runs.
Miguel Olivo hit a home run and drove in three runs for the Rockies.
Reliever Doug Slaton (1-0) pitched in the seventh and picked up the win.
Jhoulys Chacin (2-1) was the loser, allowing six runs and six hits in five innings.
Copyright 2010 United Press International.