Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 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 in preheated oven until a toothpick inserted into center of cake comes out clean, 50 to 60 minutes. Allow to cool in pan for 15 minutes before inverting onto a wire rack to cool completely. Before serving, 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.