[beaversmom]

I kinda figured what Zip meant, but had to look up to be sure:

https://books.google.com/books?id=HRsWBAAAQBAJ&pg=PA167&lpg=PA167&dq=zip+slang+vietnam&source=bl&ots=sTzuONJ7jt&sig=RUvQP4qsc-7laRHU88G7tvE0uwQ&hl=en&sa=X&ved=0ahUKEwintqSi4pPLAhVDyWMKHaX3AQAQ6AEIMDAD#v=onepage&q=zip%20slang%20vietnam&f=false

[Little Bill]

That was a Korean War thing, it was popular in the earlies before the term Gook became pejorative of choice.

Orientals have a slant to their eyes that resembles the prongs on a Zipper. Zap is to get dead, as in we got ambushed yesterday and three guys got Zapped and eight got dinged, wounded,

[Kenton]

If I remember correctly, “Zip” was short for “Zipperhead”, another term of endearment.