Preheat the oven to 350 degrees. In a bowl, combine flour, baking soda, salt, cinnamon and cocoa powder and whisk or sift to combine. In a mixer or mixing bowl, combine the butter, vanilla extract and sugar and mix until creamy. Add the egg and shredded zucchini and mix just until combined. Pour in the flour mixture (I typically do this in thirds) and mix just until combined. Add the chopped walnuts and chocolate chips, mix to integrate into dough.