Preheat oven to 350°
Grease and flour two 9" round cake pans. Set aside.
In a large mixing bowl, whisk flour, cocoa powder, salt, baking powder, and baking soda together. Set aside (sugar will be added to wet ingredients).
In a medium mixing bowl, whisk vegetable oil, water, avocado, white vinegar and vanilla until combined.
Add sugar to wet ingredients and mix well, by hand with whisk.
Pour wet ingredients into dry ingredients and mix well with a spoon or a whisk until combined.
Stir in zucchini.
Pour into prepared cake tins and bake for approximately 30-35 minutes or until toothpick comes out clean.
Remove from oven and place on a cooling rake. Remove from pans after 15 minutes and let cake cool completely before frosting.