Longtime pals and business partners Steven Spielberg, 55, and Robert Zemeckis, 49, whose collaborative efforts include the “Back to the Future” movie series, are looking to sever their business ties, reports Variety. As the two have been friends for nearly 30 years, the news is raising several eyebrows in Hollywood. Zemeckis’s production company, Imagemovers, which called Spielberg’s DreamWorks studio home for the last four years, is now “in serious discussions” to move to Warner Bros. Pictures, reports Variety. (Warner Bros., like PEOPLE.com, is owned by AOL Time Warner.) As a director, Zemeckis’s pictures include “Forrest Gump” (for which both he and star Tom Hanks won Oscars) and “Cast Away” (again starring Hanks). The latter was coproduced by DreamWorks and 20th Century Fox, which shared in the profits. DreamWorks has reportedly spent a lot of money on Imagemovers, building it an office building and developing a number of projects that have yet to reach fruition. (DreamWorks could not be reached for comment.) These factors may account for DreamWorks’s permission to allow Zemeckis to shop around for a new home, Variety notes. Only question: Who will get custody of both filmmakers’ trademark baseball caps?