Preheat oven to 375°F.
Cook lasagna noodles until just tender.
Heat olive oil in a skillet.
Sauté shallots and garlic briefly.
Add shrimp and scallops.
Cook until just opaque.
Gently fold in crab meat.
Remove seafood from heat.
Melt butter in a saucepan.
Whisk in flour until smooth.
Slowly add milk and cream.
Cook until sauce thickens.
Season with salt, pepper, nutmeg.
Stir in Parmesan cheese.
Mix ricotta with herbs and zest.
Spread sauce in baking dish.
Add noodles, seafood, ricotta.
Repeat layers evenly.
Finish with sauce and mozzarella.
Cover with foil and bake 30 minutes.
Uncover and bake 15 minutes more.
Rest before slicing and serving.