I don't know of how much interest film-score is to the common FincherFanatic but I personally have always been a great fan of film music and the synthesis of it with the moving picture. And even though ZODIAC is not the perfect example for an orchestral score the likes that John Williams or Hans Zimmer have been putting out (merely due to its lack of recognizable melodies and themes), it is a very well done one that supports the film and gives it mood and depth.
When searching for an interview with David Shire I had found several comments that point to a much more in depth talk about his work on ZODIAC, using excerpts from the score and running a total of two hours! Unfortunately I coulnd't locate that interview anywhere.
What I have, though, is this audio interview conducted by Tommy Pearson in July 2007 for Stage & Screen Online. You can listen to the interview on their website or download an mp3 version of it.
David Shire has written scores for such films as "All The President's Men" (1976), "Short Circuit" (1986) and won the Academy Award for Best Score for 1979's "Norma Rae".
In this interview Shire talks about his collaboration with David Fincher beginning at 32:59. Enjoy: