"Z" is looking like a prefix for something.
ZASH (Shale's Soul-Name) = ?-THING?
Zarhan Fast Fire = Z-AR-HAN = ?-
If this gets too troublesome it looks like the word for thing "ASH" will have to change.
I'm thinking Z is the prefix meaning "UN" or some other form of negation.
Looking at ZARHAN, a character which I know little about, could be seen as "UN-SKILLED-?" HAN might mean "speak" or "voice" perhaps.