If I'm correct, and I may not be, the term "Zips" is used for Italian/Sicilian mafiosi who are specifically brought here by an American mafia family to murder somebody higher up in another family. They are quickly brought in and quickly shipped out after the "job" is completed. The big attraction is that the target does not recognize these guys let alone consider them a threat. Remember when Tony Soprano had "Zips" come over and try to kill Phil Leotardo? They posed as DHL delivery men and shot the wrong guy and his daughter. I think they are called "Zips" whether they come from the Naples Commora or the Corleonesi in Sicily.