Preheat oven to 350°. Oil and flour a 4- by 8-in. loaf pan. Whisk 2 cups flour with other dry ingredients (except sugars) in a bowl.
Beat sugars, eggs, and 1/2 cup oil until blended. Slowly mix in zucchini. Gradually beat in flour mixture until just combined.
Scoop batter into pan. Bake until a toothpick inserted in the center comes out clean, about 1 hour. Cool 10 minutes, then invert onto a rack. Turn over; let cool completely.
Note: Nutritional analysis is per slice.