Am I correct in assuming that "Z" is the reward travel class for CO flights to HNL?

I'm looking at random dates in March from LAX and they're Z9 across the board. I find it hard to believe that if I were to call I would be allowed to book such a seat.

How does the "E" class relate to reward seats/upgrades on this route? Can I extrapolate some other availability information from the E class?