Prep: Preheat oven to 350 degrees Fahrenheit. Line a loaf pan with parchment papers or spray with cooking spray.
Shred: Using a grater, shred the zucchini until it fills one packed cup. Do not strain the liquid out of the zucchini. The additional moisture is needed for the bread.
Mash: In a large bowl, mash the ripe bananas with a fork until there are no more large chunks.
Add ingredients: To the bowl with the mashed bananas, add the egg, oil, maple syrup, vanilla, cinnamon, baking powder, baking soda, and salt. Stir to combine.
Add flour and zucchini: Add the flour to the bowl and gently stir to combine. Add the shredded zucchini to the bowl and stir until evenly incorporated.
Bake: Transfer the mixture to the loaf pan. Bake for 45-50 minutes or until a toothpick inserted into the middle of the bread comes out clean. Let the bread cool in the pan for 10 minutes, then remove and place on a cooling rack.