Peel, wash and cut the potatoes into round slices. Wash the zucchini and cut into thick slices.
Put a layer of potatoes in a medium-sized casserole dish and season with salt and pepper. Place a layer of zucchini on top of the potatoes, also season with salt and pepper. Sprinkle with half the amount of finely chopped parsley and three finely chopped cloves of garlic. Chop the tomatoes. Place half of the tomatoes on the zucchini. Then put another layer of potatoes and zucchini on top. Top with the rest of the parsley, garlic and tomatoes. Season with salt and pepper. Pour 1.5 cups of hot water and the oil over everything.
Bake in a hot oven at 180 ° C top / bottom heat for one hour, then leave to stand in the open oven for 15 minutes.