Lightly coat the sea scallops in flour seasoned with salt and pepper. Discard remaining flour.
Preheat a large skillet over medium high heat. Add oil (1 turn around the pan) and butter. When butter melts into oil, add scallops. Brown scallops 2 minutes on each side, then remove from pan.
Add an additional drizzle of olive oil to the pan and add the garlic, shallots, and crushed red pepper flakes. Reduce heat a little and saute garlic and shallots 2 minutes, stirring constantly. Add wine to the pan and free up any pan drippings. Reduce wine 1 minute, then add stock, tomatoes and saffron threads. When liquids come to a bubble, add shrimp and cook 3 minutes. Return scallops to the pan and cook shrimp and scallops 2 to 3 minutes longer. Transfer shrimp and scallops to a warm serving dish and top with basil and lemon zest. Pass plenty of bread to enjoy the juices.