Complex sentence: Her major work was with Kalyanji Anandji for whom she sang many hit songs in the 1970's most of them duets with Mohammed Rafi.
Split into simpler sentences: Her major work was with Kalyanji Anandji for whom she sang many hit songs. She continued to croon one to another hit tracks under Kalyanji Anandji in the 1970's and sang mostly duets with Mohammed Rafi.