Bring a large pot of water to a boil. Add pasta and cook until just tender, 8 to 10 minutes, or according to package directions. Drain and rinse.
Meanwhile, heat oil in a large skillet over medium heat. Add garlic and shallot and cook, stirring, until beginning to soften, about 1 minute.
Increase the heat to medium-high. Add tomatoes, wine, salt and pepper. Bring to a simmer and cook for 1 minute. Add clams, cover and cook for 2 minutes. Stir in scallops, fish and marjoram. Cover and cook until the scallops and fish are cooked through and the clams have opened, 3 to 5 minutes more. (Discard any clams that don¿t open.)
Spoon the sauce and clams over the pasta and sprinkle with additional marjoram and Parmesan (if using).