This scene had some incredible shots.
If i was the one directing this scene i think i would have treated the Zodiac killer (the person on the phone) like HAL from 2001: A Space Odyssey. He’s just a voice without a face and hes our ominous, menacing antagonist of the film. I would have tried to focus in on the monitor, the one Melvin Belli is talking and staring into, and tried to convince the audience this was him. Maybe i’d show off the red tint of the recording light to set the mood. The color red is often used as a technique to set the tone of the shot.