Trevor Lewis also scored and Peter Budaj made 21 saves for the Kings, who raced to a 4-0 lead early in the second period with a rare offensive burst from one of the NHL's lowest-scoring teams.
Los Angeles chased Jake Allen with Muzzin's second goal, sending the St. Louis goalie to the bench early in his second straight game.
Paul Stastny scored on a skate deflection for the Blues, who have lost four of six. Carter Hutton replaced Allen and gave up two quick goals to Pearson.
