Complex sentence: Eventually, Westinghouse agreed to a long-term affiliation contract with CBS, resulting in WJZ-TV and its sister stations in Philadelphia and Boston switched to CBS (Westinghouse's two other television stations, in Pittsburgh and San Francisco, were already CBS affiliates).
Split into simpler sentences: Eventually, Westinghouse agreed to a long-term affiliation contract with CBS. As a result, WJZ-TV and its sister stations in Philadelphia and Boston switched to CBS (Westinghouse's two other television stations, in Pittsburgh and San Francisco, were already CBS affiliates).