Preheat oven to 375°F
Line a baking sheet with parchment paper and set a cooking rack on top.
Cut each zucchini in half horizontally, then each section cut in half.
Scoop out the center of the zucchini, leaving about ½ inch of zucchini on the skin. Place the removed contents in a medium sized bowl.
Dice the removed zucchini centers into small pieces.
Add cooked ground sausage, Italian seasoning, salt and pepper to the bowl with the diced zucchini. Stir in marinara sauce.
Fill each zucchini boat with the mixture and sprinkle with mozzarella cheese.
Place into oven and bake until the zucchini is tender, and the cheese has melted, about 15 minutes.
Remove from oven and garnish with Parmesan.