It will be the first time both musicians have worked on the awards broadcast, which ABC will air Feb. 26, the Academy said.
Zimmer won the best score Oscar in 1995 for his work on "The Lion King." He's received eight other nominations, most recently for 2010's "Inception."
Although Zimmer has scored five films this year – ranging from the comedy "The Dilemma" to the animated movies "Rango" and "Kung Fu Panda 2" to the sequels "Pirates of the Caribbean: On Stranger Tides" and "Sherlock Holmes: A Game of Shadows" – he told the Hollywood Reporter in October that he planned to sit out any personal Oscar campaigning this year, saying "I just wanted to take a step back and say 'I'm not in the race'."
The Grammy-winning Williams composed the score for the 2010 animated movie "Despicable Me" and his songs have appeared in such films as "Fast & Furious," "The Brave One," "Knocked Up" and "Mean Girls."
– The Hollywood Reporter