Preheat oven to 350°.
. Combine 2 tablespoons brown sugar, walnuts, and 1/4 teaspoon cinnamon in a small bowl. Set aside.
. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, remaining brown sugar, remaining 3/4 teaspoon cinnamon, baking powder, and next 4 ingredients in a large bowl; make a well in center of mixture.
. Combine zucchini and next 6 ingredients in a medium bowl; add to flour mixture. Stir just until moist.
. Spoon batter into an 8 x 4-inch loaf pan coated with cooking spray. Sprinkle walnut mixture evenly over batter.
. Bake at 350° for 50 minutes or until a wooden pick inserted in center comes out almost clean. Cool 5 minutes in pan on a wire rack; remove from pan. Cool completely on wire rack.