Complex sentence: The success of the first "High School Musical" film led Tisdale to reprise her role in the 2007 sequel "High School Musical 2"; it became the most-watched cable-television movie, with 17 million viewers on its premiere.
Split into simpler sentences: The success of the first "High School Musical" film led Tisdale to reprise her role in the 2007 sequel "High School Musical 2". Even more successful than the first film, "High School Musical 2" became the most-watched cable-television movie, with 17 million viewers on its premiere.