Do not underbake the cake; the zucchini adds moisture requiring longer baking time than usual chocolate cakes. Use the toothpick test to check doneness., When baking in a Bundt pan, add about 5 extra minutes to baking time and use nonstick spray with flour to prevent sticking., For a lighter frosting option, use a powdered sugar glaze, especially on Bundt cakes., Use unpeeled zucchini for extra color and nutrients unless the skin is very tough, then peel before grating., Substitutions: swap chocolate chips for chopped walnuts or other nuts; replace vegetable oil with unsweetened applesauce for lower fat; use a gluten-free flour blend to make gluten-free; add 1 teaspoon instant espresso powder to dry ingredients for enhanced chocolate flavor; use Dutch-processed cocoa mixed with natural cocoa for variation., Storage: Cake stays moist up to 3 days refrigerated, wrapped tightly. It freezes well wrapped in cling wrap and freezer bags; thaw in the refrigerator before serving., For dairy-free substitutions, use dairy-free butter and non-dairy milk mixed with vinegar to mimic buttermilk., For egg replacements, use commercial egg replacer or flaxseed and water mixture per egg.