Preheat oven to 375 degrees. Place muffin liners in muffin pan and set aside.
Mix sugar, oil and vanilla together in a large bowl. Add eggs one at a time, whisking well between each addition. Whisk in Greek yogurt. Stir in zucchini.
In a small bowl, add flour, cocoa, baking soda and salt. Stir together.
Add flour mixture to wet ingredients and stir to combine. Stir in chocolate chips. Use an ice cream scoop to fill muffin liners. Bake for 15-17 minutes or until toothpick inserted in center of muffins comes out clean.