1Peel shrimp. (If shrimp are frozen, do not thaw; peel in cold water.) Make a shallow cut lengthwise down back of each shrimp; wash out vein.
2Mix shrimp, scallops, zucchini, yellow squash and bell pepper in 3-quart microwavable casserole. Cover tightly and microwave on High 8 to 10 minutes, stirring every 3 minutes, until shrimp are pink and firm. Drain; let stand covered 5 minutes.
3Mix broth, lemon juice, cornstarch, dill weed and salt in 2-cup microwavable measuring cup until smooth. Microwave uncovered on High 3 to 4 minutes, stirring every minute, until mixture thickens and boils. Stir into seafood mixture.
4Serve seafood mixture over pasta. Garnish with additional fresh dill weed if desired.