Preheat oven to 350 degrees F (175 degrees C). Grease and flour Bundt pan.
In a medium bowl, sift flour, cocoa, baking powder, baking soda, salt and cinnamon. Set aside.
In a large bowl, cream butter and sugar until fluffy.
Add eggs, 2 teaspoons vanilla and milk to the butter mixture. Stir in dry ingredients and mix until well blended. Fold in zucchini, orange zest and nuts.
Pour into a greased and floured Bundt cake pan.
Bake at 350 degrees F (175 degrees C) for 50 to 60 minutes, or until a toothpick inserted into center of cake comes out clean. Allow to cool, then drizzle with glaze.
To make the glaze: In a small bowl mix together sugar, orange juice and 1 teaspoon vanilla. Invert cake onto serving dish, then pour glaze over.