In a large skillet on medium, heat oil. Add shallot and garlic and cook, stirring, just until tender, about 2 minutes. Stir in tomatoes and cook, stirring often, just until softened, about 3 minutes. Stir in sardines and cook for 1 minute.Add zucchini and cook, stirring gently to avoid breaking up sardines, just until zucchini is softened, about 2 minutes. Gently stir in lemon zest.Sprinkle with basil, cheese and pepper flakes before serving.