01 - Preheat oven to 350°F. Grease and flour a 9x5-inch loaf pan.
02 - In a large bowl, whisk together the vegetable oil (or melted butter), eggs, and vanilla extract until smooth. Add the mashed bananas and grated zucchini, mixing until evenly incorporated.
03 - In a separate bowl, whisk together the all-purpose flour, granulated sugar, salt, baking soda, baking powder, and ground cinnamon until well distributed.
04 - Gradually fold the dry ingredient mixture into the wet ingredients until just combined. Be careful not to overmix, as this can make the bread dense.
05 - Gently fold in chopped walnuts, pecans, or chocolate chips if using, distributing them evenly throughout the batter.
06 - Pour the batter into the prepared loaf pan and smooth the top with a spatula for an even surface.
07 - Bake for 50 to 60 minutes, or until a toothpick inserted into the center of the loaf comes out clean. Check at the 50-minute mark to avoid overbaking.
08 - Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.