Preheat the oven to 375°F, line a muffin pan with cupcake liners, and set aside. If you don’t want to use liners, you can just grease the muffin pan with vegetable oil or non-stick spray.
In a mixing bowl, mix dry ingredients (whole wheat flour, cocoa powder, baking soda, baking powder, cinnamon, and salt).
In a large mixing bowl, whisk together wet ingredients (vegetable oil, apple sauce, eggs, sugar, and vanilla extract).
Add dry ingredients to wet ones and fold it in.
Wash zucchini thoroughly and grate, using a large grater. Squeeze the juices through a cloth or a clean towel.
Add grated zucchini and chopped walnuts, and fold it in.
Divide the mixture between 12 muffin tins. Bake at 375°F for about 20-25 minutes, or until a tooth pick inserted in the middle comes out clean.
Take them out of the oven and let sit on the counter in a muffin pan for about 10 minutes, then transfer to a wire rack to cool off completely.