Fry bacon in heavy stock-pot; remove, drain, crumble, then set bacon aside.
Saute onion, celery, and carrots in stockpot in a small amount of reserved bacon fat; add mushrooms and zucchini and continue sauteeing for 2 minutes.
Add water; cover stock pot and simmer until vegetables are tender.
Add corn, peas, mashed potatoes, and milk and heat through.
Add cheese and stir until melted; season, and serve hot.
*Note:For this recipe I like to use mashed potato flakes prepared according to package directions using 2 2/3 c water, 1/4 c margarine, 1 tsp salt, 1 c milk, and 2 2/3 c potato flakes to make 3 1/3 cups/8 servings.