The movie is directed by David Fincher whom directed such movies as Fight Club and Panic Room. I have always liked his style of directing and this movie is no exception. The movie is brilliantly cast with Jake Gyllenhaal, Robert Downey Jr. and Mark Ruffalo. The movie also has Anthony Edwards and Adam Goldberg. If there is one thing this movie should be noted for, it's the acting. Almost every person in this film did a good job and the three leads did what I thought to be, Oscar worthy performances. Mark Ruffalo did an exceptionally good job and I think he should win an Oscar one of these days.
That being said, there are parts where the story does seem to drag. This movie is 2 hours and 40 minutes long and sometimes you can feel it but I never really lost interest in it. I think if this movie had been acted with shitty actors it would of been a bomb but it wasn't. David Fincher's lighting and cinematography were also well done I thought. The movie makes an interesting case on who the Zodiac might be. Who knows, he may still be out there. Just watch this movie and see.
That being said, this is not David Fincher's most entertaining movie but it does seem like his most ambitious movie to date. It seems like he is stepping it up a notch on what he can do as a director. I think he did a good job overall.
That being said, I would give this movie about 3.35 stars out of 4. I don't feel it is a masterpiece but it isn't a bad movie either. And it did keep my attention.

Mark Ruffalo was notorious for taking out low angle cameras with car doors. This movie was no exception.

Mark: "No I will not re-enact the Brokeback Mountain scene with you"
Jake " I wish I knew how to quit stu."