Final answer:
The director's producing partner in Hollywood and co-producer of Sunset Boulevard was the character Max.
Step-by-step explanation:
The question relates to the movie Sunset Boulevard, which is a classic film from Hollywood's Golden Age. The director's producing partner and co-producer of the movie is none other than the character Max, who was also a former director and husband to the film's protagonist, Norma Desmond. Norma Desmond is a faded silent movie star, and the protagonist is Joe Gillis, a struggling screenwriter. The story revolves around their complex relationship, with Max silently supporting Norma's delusions of a comeback.