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 vegetable oil (or melted butter), eggs, and vanilla extract until smooth. Fold in the mashed bananas and grated zucchini, mixing until evenly distributed.
03 - In a separate bowl, whisk together the all-purpose flour, granulated sugar, salt, baking soda, baking powder, and ground cinnamon until well combined.
04 - Gradually add the dry ingredient mixture to the wet ingredients, folding gently until just combined. Avoid overmixing to keep the bread tender.
05 - If using, gently fold in the chopped walnuts, pecans, or chocolate chips until evenly dispersed throughout the batter.
06 - Pour the batter into the prepared loaf pan and use a spatula to smooth the top into an even layer.
07 - Bake on the center rack for 50 to 60 minutes, or until a toothpick inserted into the center of the loaf comes out clean.
08 - Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing into portions.