Prep your pan and oven. Heat the oven to 350°F (175°C). Line a 12-cup muffin pan with paper liners or grease it lightly.
Grate the zucchini. Use the fine holes of a box grater.
Gather the shreds in a clean towel and gently squeeze—don’t wring them dry, just remove the wettest liquid.
Whisk dry ingredients. In a medium bowl, whisk flour, baking powder, baking soda, salt, and cinnamon until evenly combined.
Mix the wet base. In a large bowl, whisk Wowbutter, brown sugar, and granulated sugar until smooth. Add the eggs and whisk until glossy. Stream in the oil, milk, and vanilla, and whisk until fully blended.
Combine wet and dry. Add the dry ingredients to the wet bowl.
Stir gently with a spatula until a few streaks of flour remain.
Fold in zucchini and add-ins. Gently fold in the grated zucchini and any optional mix-ins. Do not overmix. The batter will be thick but scoopable.
Portion and top. Divide the batter among the muffin cups, filling each about 3/4 full.
Sprinkle with coarse sugar or a few pumpkin seeds if you like.
Bake. Bake for 18–22 minutes, until the tops spring back and a toothpick comes out with a few moist crumbs.
Cool. Let muffins rest in the pan for 5 minutes, then move to a rack to cool completely. They set up as they cool and taste even better after 30 minutes.