Preheat the oven to 400℉. Line a muffin tin with muffin liners or spray with cooking spray.
In a small mixing bowl, add the grated zucchini (juice and all), eggs, sugar, and melted butter. Stir together to combine. Set the bowl to the side and allow it to rest for 5 minutes. You will notice a sort of 'froth' layer on top and that's what we want to happen.
Add the dry ingredients into the wet ingredients bowl and stir gently, with a wooden spoon or spatula, just until combined and no flour streaks or pockets remain in the batter.
Scoop the muffin batter into each muffin liner, filling each one about 2/3 of the way full (slightly over halfway).
Bake for 12-17 minutes or until they begin to get golden brown and a toothpick inserted into the center comes out with crumbs on it and not wet batter. You can also lightly touch the top of a muffin and it should spring back when they're properly cooked.
Remove the muffins from the oven and let them cool in the warm pan for 10 minutes before removing them to a cooling rack to cool completely, or eat one warm!
Notes
Butter : If using unsalted butter then you may want to add some salt in with the dry ingredients. I would use 1/4-1/2 teaspoon of kosher salt or sea salt. 12 tablespoons of butter is equal to 1 stick + 1/2 stick of butter or also 3/4 cup butter. Zucchini : Use a cheese grater to grate the zucchini. You can use either the fine side of the grater or the larger/coarser side of the grater. I prefer the fine side so the shreds of zucchini are smaller and harder for my kids to see! Make sure to not drain the juices from grating the zucchini. Add the shredded zucchini + all the juices into the mixing bowl.