Prep the oven and pan: Preheat your oven to 350°F (175°C). Grease a 12-cup muffin tin well with cooking spray or a thin layer of olive oil.
You can also use silicone liners to prevent sticking.
Grate and drain the zucchini: Use the large holes of a box grater. Place the grated zucchini in a clean kitchen towel or paper towels and squeeze out as much moisture as you can. This step is crucial for preventing soggy muffins.
Cook aromatics (optional): If using onion or raw sausage, sauté in a small skillet over medium heat with a bit of oil until soft and lightly golden. Let cool slightly.
Whisk the eggs: In a large bowl, whisk eggs with heavy cream, salt, and pepper until smooth and slightly frothy.
Stir in garlic, smoked paprika, and herbs.
Add the mix-ins: Fold in the drained zucchini, shredded cheddar, Parmesan, and any cooked bacon or sausage. Mix just until combined.
Fill the muffin tin: Divide the mixture evenly among the 12 cups, filling each about 3/4 full. Give the tin a gentle tap on the counter to settle the mixture.
Bake: Bake for 18–22 minutes, or until the centers are set and the tops are lightly golden.
A toothpick should come out mostly clean.
Cool and release: Let the muffins rest in the pan for 5 minutes, then run a thin knife around the edges and lift out. Transfer to a rack to finish cooling or enjoy warm.