Bring a large pot of salted water to a rolling boil. Carefully add the jumbo pasta shells and cook until al dente, about 9–11 minutes. Drain and rinse under cold water.

In a medium saucepan, melt butter and olive oil over medium heat. Add minced garlic and sauté until fragrant, about 1 minute. Stir in cream cheese until melted, then blend in heavy cream. Simmer for 2-3 minutes, then mix in Parmesan cheese, Italian herbs, lemon zest, salt, and pepper to taste.

In a large mixing bowl, combine crab meat and chopped shrimp. Add ricotta cheese, shredded mozzarella, and 1/4 cup of the creamy sauce. Season with salt, pepper, and optional red pepper flakes. Stir until well incorporated.

Using a spoon or small ice cream scooper, fill each cooled pasta shell with seafood mixture, placing filled shells on a plate or baking dish.

Preheat your oven to 375°F (190°C). Grease a baking dish with olive oil. Pour a thin layer of creamy sauce on the dish bottom, arrange stuffed shells, then pour remaining sauce over them. Top with extra Parmesan. Cover with aluminum foil.

Bake for 20 minutes covered. Remove foil and bake for an additional 10 minutes until golden brown and bubbling.

Allow shells to cool for a few minutes, then sprinkle with chopped parsley before serving.