Simplify the following text for a Grade 9 native English-speaking person.
Original: His third operetta , Die Fledermaus ( 1874 ) , became the most performed operetta in the world , and remains his most popular stage work .
Simplified: Straussâ s operetta Die Fledermaus ( â The Batâ ) has been performed more than any other operetta . In Spain the Zarzuela was a kind of operetta .