Preheat the oven to 325 degrees F (165 degrees C). Grease and flour two 8x4-inch bread loaf pans.

Beat eggs in a large bowl with an electric mixer until light yellow and frothy. Add white sugar, zucchini, oil, bananas, brown sugar, and vanilla; beat until well combined. Stir in flour, cinnamon, baking powder, baking soda, and salt. Fold in cranberries and nuts if using. Divide batter evenly between the prepared loaf pans.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 45 to 50 minutes. Allow to cool in the loaf pans on a wire rack before removing and serving.