Preheat oven to 425℉.
Add diced potatoes and zucchini to a large sheet pan. Drizzle with olive oil and toss to coat. Sprinkle with salt, pepper and cumin. Bake in preheated oven, tossing occasionally, until tender.
Brown ground beef and drain. Add taco seasoning and water and combine.
Remove potatoes and zucchini from oven. Top with taco meat. Sprinkle with shredded cheese and return to the oven until the cheese melts. (watch closely)
Remove from oven and serve. Top each serving with sour cream, pico or salsa, and guacamole, if desired.
