Preheat your oven to 350°F (175°C) and prepare a 9x5-inch loaf pan by greasing it or lining it with parchment paper.

In a medium bowl, whisk together the all-purpose flour, baking soda, baking powder, cinnamon, nutmeg, cloves, and salt.

In a large bowl, beat the granulated sugar and vegetable oil for about 2 minutes until fluffy. Slowly add eggs and vanilla extract, mixing continuously.

Gently mix in the pumpkin puree until fully integrated, then fold in the grated zucchini.

Gradually add the dry mixture to the wet mix and gently fold together until just combined.

If using, fold in the chopped walnuts or pecans.

Pour the batter into the prepared loaf pan, smoothing the top evenly.

Bake for 60-70 minutes until a toothpick comes out clean or with a few moist crumbs.

Let the bread cool in the pan for about 15 minutes before transferring to a wire rack to cool completely.