He collaborated with Leo Stein to produce the libretto of Franz Lehár's romantic operetta The Merry Widow (Die lustige Witwe).
Alas, Simplicius, a story of the Thirty Years' War, produced at the Theater an der Wien on 17 December 1887, was scarcely a success, even after being revised twice.
There followed a string of further creations with composers such as Zamara, Joseph Hellmesberger, Jr., Alphons Czibulka, Rudolf Dellinger, and even Franz von Suppé (his last work, Das Modell), as well as German adaptations of foreign works that included Arthur Sullivan's The Yeomen of the Guard and Edward Jakobowski's Erminie.
It was Lizzi who suggested the Chinese setting for Die gelbe Jacke, later revised as Das Land des Lächelns.
Léon remained active well into the 20th century, providing the libretto for Lehár's Das Land des Lächelns (1930), among other works.