Just to state the fact, E stands for the German word entgangen
, which means opposite. Z stands for zusammen
, which means together. That helps me remember how the two work together. I also hate stereochemistry
it's never really been one of my strong points.
Oh, and the reason that you would use the E/Z system rather than cis-trans is because the priority groups can be ambiguous. If you can name it cis/trans without a doubt, and in a way that would not be confusing to other chemists, then go for it. But if it seems like it might be confusing to other chemists out there, go for the E/Z system. It's always a nice fallback.
And correct me if I'm wrong, but double bonds essentially count as two carbons, correct? Not atomically or anything, just when you're adding up the carbons.