I may be an ignoranimous, but I don't think there's a Jewish zodiac. I believe there were twelve tribes in old Israel, from which modern Jews are supposed to be descended. Those may be their symbols.
Another possibility: although there were originally only twelve tribes, the limits on additional tribes were never clearly delineated. As a result, modern Jews were given the option to create new tribes when the need arose. This created great angst amongst the older Jews, believing that they were in limited-edition tribes, but---what the hey. It seems that rules were made to be broken----and it appears that the appearance of a new tribe every now and then can lead to casinos---and you know what that means:
more chips! I don't want to be accused of racial profiling, but anyone carrying a loose kreplach deserves a closer look, if you ask me.
I'm certainly happy to be able to help in clearing up any confusion here.