Simplify the following text for a Grade 9 native English-speaking person.
Original: In the 1971 20th Century Fox film Escape from the Planet of the Apes , the characters Zira and Cornelius are briefly quarantined at the Los Angeles Zoo .
Simplified: In the 1971 20th Century Fox film Escape from the Planet of the Apes , the characters Zira and Cornelius are briefly kept at the Los Angeles Zoo .