01 - Preheat oven to 350°F. Grease and flour a 9x5-inch loaf pan, ensuring even coverage on all sides.
02 - In a large bowl, whisk together the vegetable oil (or melted butter), eggs, and vanilla extract until smooth. Fold in the mashed bananas and grated zucchini, mixing until well incorporated.
03 - In a separate bowl, whisk together the all-purpose flour, granulated sugar, salt, baking soda, baking powder, and ground cinnamon until evenly distributed.
04 - Gradually fold the dry ingredient mixture into the wet ingredients using a spatula, stirring just until combined. Avoid overmixing to keep the crumb tender.
05 - Gently fold in chopped nuts or chocolate chips if desired, 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 on the center rack for 50 to 60 minutes, or until a toothpick inserted into the center comes out clean and the top is golden brown.
08 - Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing into even portions.