Combine zucchini, tomatoes, and olive oil in a saucepan over medium-low heat; cook and stir until zucchini and tomatoes are tender, 15 to 20 minutes. Drain liquid from saucepan.
Lightly beat egg yolks in a bowl until smooth; mix in sour cream, flour, and herb seasoning blend. Beat egg white in a separate bowl until thickened; fold into sour cream mixture.
Preheat oven to 350 degrees F (175 degrees C). Grease an 8x10-inch baking dish.
Layer 1/2 of the zucchini mixture, 1/2 of the sour cream mixture, 1/2 of the bacon, and 1/2 of the Cheddar cheese, respectively in the prepared baking dish. Repeat layering with remaining ingredients and top with French-fried onions.
Bake in the preheated oven until set and bubbling, about 30 minutes.