Preheat oven to 350 degrees. Coat two 4 1/2-by-8 1/2-inch loaf pans with nonstick spray, line with parchment paper, and spray paper. Combine zucchini, sugars, oil, and eggs in a large bowl and mix until combined. Add dry ingredients and mix well. Fold in nuts and extract. Divide batter between loaf pans. Bake until a tester inserted in the middle of each loaf comes out clean, about 1 hour 10 minutes. Cool 10 minutes on wire rack. Invert, and remove parchment paper. Cool completely on rack.