Preheat oven to 350°F. Line 2 muffin tins with cupcake liners. (I made 16 muffins.)
In a large bowl or the bowl of a stand mixer, combine oil, sugar, and vanilla. Mix on medium speed until smooth, about 1-2 minutes.
Add the flour, cocoa, baking soda, baking powder, and salt. Mix on low speed until just combined.
Fold in the zucchini, chocolate chunks, and peanut butter chips.
Scoop about 3 tablespoons of batter into each cupcake liner. Top with a few (3–5) extra chocolate chunks and peanut butter chips, if desired.
Bake for 25–30 minutes, or until a toothpick comes out mostly clean.
Let the muffins cool in the pan for about 5 minutes before transferring to a wire rack to cool completely.