In a small skillet, cook the chorizo on your stovetop until almost done, about 10 minutes. Set aside.
In a medium ovenproof (preferably cast-iron) skillet, heat oil over medium heat and cook onion and serrano, stirring, until tender, about 5 minutes. Add zucchini and corn, cooked chorizo, and cook until zucchini and corn are tender, about 7 minutes more.
In a bowl, whisk eggs with salt and oregano and pour into skillet with vegetables. Cook until sides are just beginning to set, 2 to 3 minutes.
Transfer skillet to oven and broil until just set in the middle and lightly golden and puffed on top, 2 to 3 minutes. Serve warm or at room temperature. Cut into wedges. Feel free to top frittata with salsa or queso fresco.
The nice thing about this recipe is that it is customizable. Feel free to eliminate the chorizo and serrano if you aren’t fond of spice.