Preheat oven to 325°F (160°C) and grease and flour two 9- by 5-inch (2 L) loaf pans. Sift together flour, cinnamon, baking powder, salt and baking soda; set aside. Using an electric mixer, beat eggs, sugar and brown sugar until fluffy. Add oil and vanilla in a slow, steady stream, mixing constantly. Stir in flour mixture alternately with zucchini, making 3 additions of flour mixture and 2 of zucchini. Stir in nuts. Pour into prepared pans and bake for 75 minutes, or until a tester inserted in the center of a loaf comes out with a crumb clinging to it. Let cool in pans on a wire rack for 30 minutes. Remove from pans while warm.