Pre-heat oven to 350 degrees F. Lightly grease large muffin pans and line with muffin cups.
In a medium bowl mix together the sugar, butter and oil. Beat in eggs, one at a time until well Incorporated. Stir in vanilla, buttermilk, zucchini and chocolate chips.
In a separate bowl mix together all of the dry ingredients. Add the liquid ingredients and mix until well combined. Spoon batter into large muffin pans. Bake in the center of the oven for about 35 minutes. Cool on a wire rack, while preparing the icing (hs note: I made these without the icing, also - don't overcook them or you will lose all the moist goodness - you want them to look almost done in the oven - they will continue to cook for a few minutes after you pull them from the oven from the residual heat).
Yields 9 large cupcakes or 20 standard cupcakes