Mix zucchini, onion, and carrots in a bowl. Add enough water to cover and soak for 15 minutes; drain.
Heat butter in a large stockpot over high heat; cook and stir zucchini, onion, carrots, garlic powder, and Italian seasoning until onion is transparent, about 7 minutes. Add tomatoes and beef bouillon to zucchini mixture; cook and stir until heated through, about 7 minutes.
Mix water, lentils, and ditalini pasta into zucchini mixture; reduce heat to medium-low and simmer until pasta is tender, 20 to 30 minutes.