I've looked high and low so apologies if this is state elsewhere in the manual or the black book.

In running z12, I see that the algorithms are labeled BB, CY, HP and VO, What do these abbreviations mean?

Guessing here BB = Black book, CY = ??, HP = HighPass, and VO, VolumeOptimized. (total guesses!)

Does anyone know what these abbreviations mean?

Is it also safe to assume that 2 of the algos are from z1 and two are from z2?