Combine the first 6 ingredients in a bowl, and make a well in center of mixture. Combine zucchini, milk, oil, and egg; stir well. Add to flour mixture, stirring just until dry ingredients are moistened.
Divide batter evenly among 12 muffin cups coated with cooking spray. Bake at 400° for 20 minutes or until golden. Remove from pans immediately, and let cool on a wire rack.