Zendaya plays a tennis pro in her upcoming movie "Challengers", and she took her prep seriously . . . becoming good enough at tennis that she did most of her own playing onscreen.

Director Luca Guadagnino says, quote, "She's wonderful.  I mean, wow.  We edited the movie and we almost actually don't use any of her double.  She's so good."

"Challengers" is described as a "sexy comedy," in which a love triangle develops when Zendaya's character coaches her player-husband for a big match against his childhood best friend . . . who's also her ex.