Preheat oven to 350 degrees F.
Cut the zucchini in half lengthwise.
Scoop out some of the insides of the zucchini.
In medium skillet, brown the sausage
In another skillet, add the olive oil, garlic, mushrooms and onion.
Saute vegetables until the onion is translucent.
Add the marinara/pizza sauce and browned sausage.
Place the zucchini into large baking dish, cut side up.
Fill each zucchini with sausage sauce mixture.
Top with black olives and mozzarella cheese.
Bake at 350 for 25 minutes.
Remove from oven and serve!