A zarzuela is a blackberry.
Zarzuela is the name of a small river north of Madrid where there are a lot of blackberry brambles.
Zarzuela Palace, the residence of the royal family of Spain, is located in that area. Originally a hunting lodge built for King Felipe IV in the early 1600s, it was later expanded into a palace.
Starting in the 1600s, Spanish playwrights created a kind of musical theater popular with the royal family. Because they were originally performed at the royal palace, they were called zarzuelas.
These musicals became all the rage in the mid-1800s, and Zarzuela Theater in central Madrid was inaugurated in 1856 to represent them. They were often comedies reflecting working-class Madrid of the day. Since then, the genre has continued to develop and is currently enjoying a revival.
“La verbena de la paloma,” is a classic Madrid zarzuela written by Ricardo de la Vega and Tomás Bretón, first performed in 1894. It is set in the La Paloma Fiesta held every August in Madrid, and the zarzuela has now become part of the fiesta celebrations. You can see a 1995 production of it here: http://youtu.be/c_XNnvmLQ1Q
There is also a recipe from Catalonia, a region in northeastern Spain, called seafood zarzuela, a mixture of fish and shellfish with sauce named after the musical form, which over the years has become a Catalan lyric theater distinct from the Madrid variety.
— Sue Burke