Pour the shredded zucchini into the center of a dish towel, cover with the towel, and press firmly to remove some of the excess moisture. Transfer the squeezed zucchini into a large bowl.
To the zucchini, add in the almond butter, coconut sugar, cacao powder, eggs, baking soda, salt, and vanilla. Stir well until a thick batter is formed, then fold in the chocolate chips, if using.
Divide the batter among the 12 baking cups, and top with a few additional chocolate chips, if desired. Bake at 350ºF until the muffins have risen and feel firm to a light touch, about 20 minutes. (Your kitchen should smell like brownies when they are done!)
Remove the pan from the oven and let them cool for at least 20 minutes before serving. You can serve them warm or cold, but I think they have the best flavor when they are at room temperature.
Leftovers can be stored in an airtight container in the fridge for up to a week.