Reduce heat to medium-high. In same skillet, melt remaining 1 tablespoon butter. Cook shallots, zucchini, carrots and pepper in butter about 5 minutes, stirring occasionally, until crisp-tender. Sprinkle with flour; cook 1 minute, stirring constantly. Stir in broth and sherry. Heat to boiling; boil 1 minute, stirring frequently, until slightly thickened. Return chicken to skillet. Stir in half-and-half; heat just until hot.