Preheat oven to 350 degrees F (175 degrees C). Butter a baking dish (size is dependent on the size of your zucchini).
Place crumbled sausage in a large, deep skillet. Cook over medium high heat until evenly brown. Drain and set aside.
Partially cook zucchini in the microwave on high for 5 minutes. Remove from the microwave and let cool for about 10 minutes. Meanwhile, in a medium bowl combine eggs, Colby cheese, cottage cheese, Italian blend cheese, onion, Italian seasoning, salt and pepper.
Slice the zucchini in half lengthwise, remove the seeds and rinse. Place both halves in prepared baking dish and sprinkle with garlic salt. Layer the sausage, tomatoes and cheese mixture in each half.
Bake in preheated oven for 40 minutes. Then broil for 5 minutes to brown the cheese.
