Heat water and lentils to boiling in Dutch oven; reduce heat.
Cover and cook until lentils are almost tender, about 30 minutes.
Stir in potatoes, onion, celery, garlic, parsley, bouillon, salt and cumin.
Cover and cook until potatoes are tender, about 20 minutes.
Stir in zucchini; cover and cook until zucchini is tender, 10 to 15 minutes.