Cook the Pasta Shells:
Bring a large pot of salted water to a boil. Cook the jumbo pasta shells according to the package directions, but keep them slightly al dente. Drain and set aside to cool.

Cook the Seafood:
In a large skillet, melt 1 tablespoon of butter over medium heat. Add the shrimp and scallops (if using) and cook for 3-4 minutes, or until opaque and tender. Add minced garlic and cook for another minute until fragrant. Remove from heat and chop the seafood into bite-sized pieces. Set aside.

Prepare the Creamy Sauce:
In the same skillet, melt the remaining butter and add the minced garlic. Sauté for about 30 seconds until fragrant. Add the heavy cream, bring to a simmer, and cook for 2-3 minutes. Stir in the cream cheese, Parmesan cheese, and mozzarella cheese. Continue stirring until the sauce is smooth and creamy. Season with salt and pepper to taste.

Combine Seafood with Sauce:
Add the cooked seafood mixture to the creamy sauce. Stir in chopped parsley and lemon zest (if using) for extra freshness and flavor. Mix well and remove from heat.

Stuff the Shells:
Carefully spoon the seafood mixture into each cooked pasta shell. Place each stuffed shell in a greased or parchment-lined baking dish.

Assemble and Bake:
Pour the remaining creamy sauce over the stuffed shells in the baking dish. Sprinkle extra mozzarella and Parmesan cheese on top. Cover the dish with foil and bake at 375°F (190°C) for 20-25 minutes. Remove the foil for the last 5 minutes of baking to allow the cheese to brown.

Serve and Enjoy:
Once baked to a golden perfection, remove from the oven and serve hot. Garnish with extra parsley if desired.