Preheat your oven to 375°F (190°C).
Shred 2 medium zucchini using a box grater or Mandoline. In a large bowl, mix the shredded zucchini with 1 tablespoon of olive oil. Season with salt and pepper to taste.
In a separate bowl, combine 8 large eggs, 1/3 cup whole milk or half-and-half, 1/2 teaspoon dried oregano, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Whisk until well combined and uniform in color.
Add the zucchini mixture to the egg mixture, stirring until well combined.
Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the finely diced onion and garlic to the skillet. Sauté until translucent and fragrant, about 5 minutes.
Pour the egg mixture into the skillet, spreading it evenly. Bake in preheated oven for 25-28 minutes or until golden and crisp. Rotate the pan halfway through baking to ensure even browning.
Let the zucchini breakfast bake cool for a few minutes before slicing and serving. Serve hot or at room temperature.
Note: The nutritional values are approximate and based on using whole eggs, full-fat cheese, and whole milk. They will change slightly based on the specific brands and ingredient substitutions you choose.