Heat oven to 450° F. In large ovenproof skillet, sauté zucchini, bell pepper, and onion in oil over medium heat, stirring frequently, until vegetables are just tender. Add garlic and cook for about a minute longer.
While garlic is cooking, combine eggs, milk, oregano, salt, and pepper in mixing bowl; beat well with whisk. Pour egg mixture into skillet; stir to allow egg to flow around and under vegetables.
Arrange daylily flowers in an attractive pattern on top. Cook without stirring for about three minutes; the top should still be moist, but the bottom should be well set.
Sprinkle feta cheese evenly over the top. Place skillet in oven; cook until eggs are set and top is puffed and bubbly, 5 to 10 minutes.
Remove from oven; cool slightly before cutting into wedges to serve.