Z system strategy codes

I've been meaning to ask if you could tell me what some of the the Z system strategy codes stand for.

So in particular :

Z1 - VO , ES, HU
Z2 - HP , CT, CY

A complete list would be ideal. Knowing would help me read the logs easier and better follow what the strategies are doing.

I searched the manual a few times but could not find descriptions.

Thanks
Jason

VO, ES, HU are variants of workshop 4 and HP, CT, CY are variants of workshop 5.