Preheat oven to 350 degrees F (175 degrees C). Grease two 9x5-inch loaf pans.
Mix flour, sugar, squash, oil, pineapple, nuts, eggs, vanilla extract, cinnamon, baking soda, salt, and baking powder together in a bowl; pour into prepared loaf pans.
Bake in the preheated oven until a toothpick inserted in the middle comes out clean, about 1 hour. Cool bread for 10 minutes in pan before transferring to a wire rack to cool completely.