Zip is a slur used to describe Italians in a derogatory way. Used by some Italian-Americans to refer to new Italian immigrants because of how fast they are able to speak the old language. The term was coined by National Enquirer founder Fortune Pope, Sr. and his friend Joe Bonanno in the 50's or 60's.
The word Zip is a racial slur that has been used historically to degrade and dehumanize italians. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to italians. If you are unsure about whether or not it is appropriate to use the word Zip, it is best to err on the side of caution and avoid using it in any situation.