Preheat oven to 350F (180C). Line a standard size loaf pan with parchment paper.
Using a box grater, grate zucchini (skin on). Set aside.
In a large mixing boil, combine flours, cocoa powder, baking soda, baking powder and sugar.
In a medium size bowl, combine wet ingredients including grated zucchini, eggs, olive oil, vanilla and maple syrup. Add wet ingredients to dry ingredients. Fold in chocolate chips and walnuts.
Pour mixture into loaf pan. Bake for 70-80 minutes until a fork inserted comes out clean. If the top is starting to burn, cover with tin foil until fully baked.
Let cool completely before slicing. Place in fridge for up to a week or freezer for up to 3 months.