Preheat oven to 350F. Line a 9×5 loaf pan with parchment paper and set aside.
In a large bowl, whisk both sugars, oil, yogurt, eggs, and vanilla until smooth. In a separate medium bowl, whisk flour, baking powder, cinnamon, nutmeg, and salt.
Add flour mixture, shredded zucchini, dark chocolate, and walnuts if using to liquid mixture, gently folding until batter is just combined.
Spread batter evenly in prepared pan. Bake zucchini bread at 350F 40-50 minutes until a toothpick inserted in center comes out clean.
Cool zucchini bread completely on a wire cooling rack. Remove bread from pan and cut into slices for serving. Enjoy!