In 4-cup microwavable measuring cup, mix sauce mix (from Chicken Helper box) and water. Microwave uncovered on High about 2 minutes or until sauce is thickened. Stir in sour cream, milk and vinegar with wire whisk until smooth; cover and refrigerate.
Fill 2-quart saucepan 2/3 full of water. Heat to boiling. Stir in uncooked pasta (from Chicken Helper box). Gently boil uncovered about 15 minutes, stirring occasionally, until pasta is tender; drain well.
In large bowl, stir cooked pasta, chicken, broccoli, zucchini and bell pepper. Spoon sauce over pasta mixture; toss to coat. Cover; refrigerate about 30 minutes before serving.