01 - Preheat oven to 350°F. Grease and flour a 9x5-inch loaf pan, ensuring even coverage to prevent sticking.
02 - In a large bowl, whisk together the vegetable oil (or melted butter), eggs, and vanilla extract until well blended. Add the mashed bananas and grated zucchini, stirring 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 uniformly combined.
04 - Gradually add the dry ingredient mixture to the wet ingredients, folding gently with a spatula 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 distributed 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. Check at the 50-minute mark to avoid overbaking.
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.