Who is Zayd from Assata: An Autobiography and what is their importance?

Zayd becomes one of Assata's close friends and is a member of the Black Panther Party. They were closely together on many Party events but have a falling-out that reveals the stress they are both under. The story begins with Zayd's death on the New Jersey Turnpike, and only through the story of Assata's life does the reader learn how important he was to her.