Preheat the oven to 350 degrees F. Lightly coat two 9-by-5-inch loaf pans with cooking spray.
In a large bowl, add the egg whites, canola oil, applesauce, sugar and vanilla. Using an electric mixer, beat the mixture on low speed until thick and foamy.
In a small bowl, stir together the flours. Set 1/2 cup aside. To the small bowl of flour, add the baking powder.
Add the flour mixture in the small bowl to the egg white mixture. Using the electric mixer on medium speed, beat until well blended. Add the zucchini, walnuts and pineapple. Stir until combined.
Adjust the batter with the remaining 1/2 cup flour, adding 1 tablespoon at a time. The batter should be thick and not runny.
Evenly divide the batter between the prepared pans.
Bake until a toothpick put into the centers of the loaves comes out clean, about 50 minutes. Let the bread cool in the pans on a wire rack for 10 minutes.
Turn the loaves out of the pans onto the rack. Let cool all the way. Cut each loaf into nine 1-inch slices and serve.