I don't know if this was intended, but according to traditional myth and legend, those four races breakdown elementally almost perfectly. Using the standard symbolism of the 4 common western elements the Zhu races listed seem to fit pretty easily as follows: 

Earth = Zhuni (might, discipline & military prowess being earthy)
Water = Xerin (grace, dancing & the larger families being quite watery)
Air = Xenkorian (cunning, and most mental faculties being traditionally airy)
Fire = Etherians (Berzerking plus red & pink skin tones being extremely firey)