Preheat your oven to 325°F (163°C). Grate the zucchini and squeeze out excess moisture.

Dice the apples into small ½-inch pieces and toss them in flour to prevent sinking.

In a medium mixing bowl, whisk together the flour, cinnamon, baking powder, baking soda, and salt.

In a large bowl, beat the eggs until pale and frothy, then mix in the vegetable oil and vanilla extract.

Add the white and brown sugars to the wet mixture and stir until smooth.

Pour the wet mixture into the dry ingredients, mixing gently until just combined.

Fold in the grated zucchini, diced apples, and optional walnuts into the batter.

Allow the batter to rest for 5 minutes.

Divide the batter into prepared loaf pans and smooth the tops.

Bake for 35–40 minutes for mini loaves or 40–60 minutes for full size, until a toothpick comes out clean.

Let the bread cool in pans for 20 minutes, then transfer to a wire rack to cool completely.