Preheat the oven. Set to 350°F (175°C). Lightly grease a standard 12-cup muffin tin or line with silicone liners to prevent sticking.
Prep the zucchini. Grate 1 medium zucchini on the fine side of a box grater.
Place in a clean towel and squeeze out as much liquid as you can. This step matters so the muffins bake up fluffy, not soggy.
Whisk the base. In a large bowl, whisk 8–10 eggs with 1/3 cup milk, salt, pepper, garlic powder, and onion powder until smooth and slightly frothy.
Add the mix-ins. Stir in the squeezed zucchini and 1 to 1 1/2 cups shredded cheese. If using extras like finely chopped bell pepper or cooked bacon, add 1/2 cup total so the muffins don’t overflow.
Fill the muffin tin. Divide the mixture evenly among 12 cups, filling each about 3/4 full. If you like, sprinkle a little extra cheese on top for a golden finish.
Bake. Bake for 16–20 minutes, until the centers are just set and a toothpick comes out clean.
The muffins will puff in the oven and settle slightly as they cool.
Cool and release. Let the muffins cool in the pan for 5 minutes, then run a thin knife around the edges to lift them out. Cooling helps them firm up and prevents tearing.
Serve or store. Enjoy warm, or let them cool completely before storing for the week.