Preheat the oven to 375 degrees F. Spray a 12-cup muffin tin with nonstick cooking spray.
In a large bowl, whisk together the eggs, half-and-half, Parmesan, salt, and pepper.
In a 10-inch saute pan, heat the olive oil over medium heat. Add the onion, bell pepper, and zucchini and saute for 5 to 7 minutes, until tender. Allow to cool slightly, then add the vegetable mixture and prosciutto to the egg mixture, stirring to combine.
Scoop the mixture into the prepared muffin cups, filling them almost to the top.
Bake for 20 to 25 minutes, until the frittatas are set. Allow to cool for 5 minutes, then remove from the muffin tin.
