

Slice zucchini into ¼ inch pieces. Lay in a single layer on a paper towel lined baking sheets, sprinkle lightly with 1/2 tsp salt. Place another baking sheet on top and press down to pull out moisture. Let stand for 30 minutes.
Preheat oven to 400° F. Grease a medium sized baking dish with softened butter. Arrange zucchini and squash slices into rows, alternating between each variety. Combine the shredded cheeses together. Sprinkle cheese over the arranged slices, reserving ¾ cup.
Add mascarpone, heavy cream, butter and garlic to a saucepan over med-low heat. Whisking until mixture is smooth, about 3 minutes. Add herbs, remaining salt and pepper to taste.
Pour mixture evenly over prepared squash. Sprinkle with remaining ¾ cup of cheese. Bake for 25-30 minutes until lightly browned on top and vegetables are soft when pierced.
Serve hot.