Preheat the oven to 350 degrees F. Line a cupcake tin with liners.
In a bowl, stir together the flour, cocoa powder, baking powder, soda and salt.
In the bowl of your electric mixer, beat the sugar and egg until slightly fluffy and combined. Add in the oil and melted butter, beating until combined. Add in the extract and beat on medium speed, scraping down the sides if needed. Add in half of the dry ingredients while beating on low speed. Add in the milk, continuing to beat on low speed then add in the dry ingredients. Beat until a smooth, silky batter forms then stir in the zucchini and chocolate chips with a spatula.
Use a 1/4 cup measure to evenly fill the liners 3/4 of the way full. Bake for 18 to 20 minutes, or until the tops are set. Let the cupcakes cool completely, the frost with the avocado frosting.