I picked up this reference from mafiatoday.com:

"For those without a mob glossary, “Zips” is street slang for the faction that includes about 25 Sicilian-born Bonanno mobsters, their relatives, and crew members – some of whom are American-born. It’s a funny word. “Zips” began as a derogative term. Some say it derives from the difficulty American mobsters have grasping the chatter of fast-speaking immigrants as it “zips” by; others say it’s a slang plural of zeros. But today, many so-called “Zips” wear the term as a “badge of honor” to describe so-called “old-school” or traditional mob values, including omerta and the use of violence whenever necessary."