Jim, I have to say you are a great contributor to this site!
You are right about the origins of these Greek surnames. Zaimis and Serdaris are indeed relics of the Ottoman Empire but Amiras is much older and dates back to the Byzantine times. Amiras does derive from Amir/Emir and it was used by the Greeks in the last centuries of the Byzantine Empire as a General's title or to address an Arab amir.
As for Zaim, I found this:
http://www.encyclo.co.uk/define/Zaim.