This is awesome!
Regarding the vertical zappers, do you mean those in the reactor? If so, there are four lights (or crosses when unlit), basically when they start lighting then the zapper on that side is about to come on, just as youll see all four lights go off when the zapper on that side goes off.
If you mean zappers on other screens, those are all predictable, just not necessarily all the same timing. In general you can stop between each zapper but it's slower.