Schwartz and Winnie Holzman are writing a musical about Princess Ozma.

Wicked composer Stephen Schwartz gave an interview backstage at Dubai Opera with The National and confirmed that he and Wicked bookwriter Winnie Holzman are at work on a new film musical.
Tentatively titled Ozma, the musical will focus on Princess Ozma and will be based on the second book in L. Frank Baum’s Wizard of Oz series, unlike Wicked, which was based on Gregory Maguire’s book.
Schwartz said in the interview that Universal is “very interested,” though no concrete plans have been made to produce the film.