Preheat oven to 325°F (165°C). Grease and flour two 8×4-inch loaf pans.
In a large bowl, beat eggs until light and frothy.
Add white sugar, zucchini, oil, mashed bananas, brown sugar, and vanilla. Beat until combined.
Stir in flour, cinnamon, baking powder, baking soda, and salt until just combined.
Fold in cranberries and walnuts if using.
Divide the batter between the two prepared pans.
Bake for 45–50 minutes, until a toothpick inserted comes out clean.
Cool in pans on wire rack before slicing.
