In stand mixer, cream together butter and sugar on medium speed.
Lower speed and add in eggs, one at a time.
Add in shredded zucchini.
Mix flour, baking soda, baking powder, salt, cinnamon, and cocoa.
Gradually add to zucchini mixture, beating well.
Add in milk, vanilla, and nuts. Beat.
Pour into greased 9x13 inch pan and bake for 1 hour at 350 degrees.