Preheat the oven to 350 degrees Fahrenheit. Grease a 9x5, or 8x4 bread loaf pan with nonstick spray, set it aside.
In a large bowl, whisk together the flour, ground cinnamon, nutmeg, baking powder, baking soda, and salt. Set it aside. 2 cups all purpose flour, 1 tsp ground cinnamon, 1/2 tsp ground nutmeg, 1 tsp baking powder, 1/2 tsp baking soda, 1/2 tsp salt
In another large bowl, whisk together the brown sugar, granulated sugar, and vegetable oil. Mix them together for a couple of minutes 1/2 cup brown sugar, 1/2 cup granulated sugar, 1/2 cup vegetable oil,
Add in the pumpkin, eggs, and vanilla extract and whisk them into the sugar until just combined. 1 cup pumpkin puree, 2 eggs, 1 tsp vanilla extract
Slowly pour the dry ingredients into the wet ingredients and stir until just smooth. Don't overmix the batter, a few lumps are okay.
Add the grated zucchini, and gently fold it into the batter.1 cup grated zucchini
Fold in any chocolate chips or walnuts, if desired. 1 cups chopped walnuts or chocolate chips
Scoop the batter evenly into the prepared loaf pan.
Sprinkle a few extra chocolate chips on top of the bread, if using.
Bake the loaves on the middle rack for 50 to 65 minutes, or until a toothpick inserted into the middle of the loaves comes out mostly clean. (A few most crumbs are okay, but no runny batter).
Remove the pumpkin zucchini bread from the oven and let it cool in pan for 10 to 15 minutes. Then remove them from the pan to cool on a wire cooling rack completely.