Although zombies aren't really the focus of Prince of Darkness, they do show up, and in fact eventually form a sizable part of the cast, so I thought I would give my two cents. Actually, since this is 2005, it's probably more like a buck now, but you know what I mean. The focus of the film is a glowing green cylinder found in a secret room by a priest, Father Loomis (Donald Pleasance). He calls in his physicist friend, Professor Birack (Victor Wong), to help identify what it is and what it's doing. Father Loomis already has a pretty good idea, though, that the cylinder is the Devil. Or what we think of as the Devil. This part is kind of muddled, but we do eventually find out that the cylinder takes people over by spraying liquid in their mouths, making them do bad things.
This movie was made in 1987, which is long enough ago that, to many people, computers were these magical objects that could do anything if you just connected enough wires between them and other things. Director John Carpenter makes heavy use of this as the professor and his grad students set up computers and other vaguely defined pieces of equipment to analyze the object. The priest and the professor sit and discuss the connection between Satan and antiparticles as the grad students (doing all the work, of course) say things like "That can't be possible!" or "How is it doing that?"
If you ignore the pseudoscience/religion, you get what Carpenter is good at, creepy images and tense moments. It turns out that once someone has been taken over by the cylinder, they can take over other people in turn by spraying into their mouths, and so on, even if those people are dead. Watching the normal characters dwindle in number as those taken over increase is the best part of the movie, but the movie gets too bogged down in it's own philosophy to really keep the pace going. If that doesn't distract you, some of the questions raised by the plot might, like, If Satan were really made of antiparticles, wouldn't he explode?
Although there are a few other notable faces in the cast (Jameson Parker and Alice Cooper, for two), it doesn't save the movie from being mostly dull. Watch it with a finger on the fast forward button.