Preheat oven to 180 C. Line a 9” cake pan with parchment paper.
Sift flour, cocoa powder, baking soda, baking powder and salt into a large bowl. Set aside.
Whisk together eggs, sugar and oil in a large bowl. Add half of the flour mixture into the egg mixture. Beat for 1 minute. Add rest of the flour and milk. Beat again for 1-2 minutes, or until combined.
Fold in grated zucchini. Pour into prepared pan, and bake for 1 hour or until a skewer inserted into the center of the cake comes out clean. Allow to cool in the pan for about 10 minutes before turning it onto a wire rack to cool completely.