1. Preheat the oven to 350° Fahrenheit (176° Celsius). Line or grease a standard size muffin tin.
2. Add the flour, cocoa powder, sweetener, baking powder, salt, and chocolate chips to a large bowl and stir very well.
3. Whisk in the wet ingredients (zucchini, eggs or water, oil, and vanilla extract) until just evenly mixed. Do not over-stir the batter.
4. Divide the mixture evenly into the muffin tin. Sprinkle more chocolate chips on top if you wish.
5. Bake on the oven's center rack for 16 minutes or until a toothpick inserted into the center comes out mostly clean.
6. Let cool, then enjoy. If you can wait, the chocolate zucchini muffins taste even more delicious the next day!
7. Once cooled, store leftovers loosely covered at room temperature overnight or in a covered container in the refrigerator or freezer for longer storage.