I found the name listed here: (
http://babynamesworld.parentsconnect.com/meaning_of_Zetta.html)
It says that Zetta is a Hebrew name, a form of Zett, and it means "in good health".
I think that Zetta could possibly also be a diminitive of names that end in -zetta, like Suzetta (form of
Suzette) or Franzetta (form of
Francette).