1. Preheat oven to 350ºF. Grease and flour two 9 x 5 inch loaf pans. Set aside.
2. In a large bowl whisk together the flour, baking powder, baking soda, salt, Cinnamon, Nutmeg, and if using chocolate chips. Set aside.
3. In mixing bowl whisk together the oil, sugars, eggs and vanilla, until well combined. Stir in the zucchini. Add the wet ingredients to the dry ingredients and mix until just blended.
4. Divide the batter between the two prepared pans. Sharply tap once on the counter to remove any air bubbles.
5. Bake for 50 minutes to 1 hour or until a toothpick comes out clean. Cool for 10 minutes in the pan, then remove bread from pans and cool completely on the wire cooling rack.
6. If making cream cheese frosting: In a stand mixer fitted with a paddle attachment or with a handheld mixer, combine all ingredients and beat until fluffy, about 4 minutes. Divide frosting between the two breads and frost as desired. Refrigerate for up to 3 days.