This cake can be frozen for up to 6 months. To make sour milk, mix 1/2 cup milk with 2 teaspoons lemon juice and let stand 10 minutes.
1 Cream together butter or margarine, vegetable oil and sugar.
2 Add eggs, sour milk, and vanilla. Blend well.
3 In a separate bowl, sift dry ingredients together.
4 Blend dry ingredients into the butter mixture.
5 Add grated zucchini, and mix well.
6 Spread in a greased floured 9 x 13 inch pan. Sprinkle walnuts and chocolate chips on top.
7 Bake in a preheated 325 degrees F (165 degrees C) oven for 45 minutes.