Preheat oven to 350°. Beat first five ingredients. Combine dry ingredients; gradually add to egg mixture and blend well. Stir in zucchini.
Fill paper-lined muffin cups two-thirds full. Bake until a toothpick inserted in center comes out clean, 20-25 minutes. Cool 10 minutes before removing to a wire rack.
For frosting, combine brown sugar, butter and milk in a large saucepan. Bring to a boil over medium heat; cook and stir until thickened, 1-2 minutes. Remove from heat; stir in maple extract. Cool to lukewarm.
Gradually beat in confectioners’ sugar until frosting reaches spreading consistency. Frost cupcakes. Yield: about 1-1/2 dozen.