zip, v.³ — Green’s Dictionary of Slang

zip v.³

[echoic of the zip sound of a bullet but note zip n.¹, i.e. one renders the target ‘nothing’]

(US) to shoot (dead); thus zipping n.

1969		D. Pendleton Executioner (1973) 63: ‘Can you safely detain them?’ ‘Not without getting detained myself. Unless you want ’em zipped.’ ‘Hell no, no zipping!’.
1990		S. Morgan Homeboy 66: Don’t zip him [...] The Troll ain’t worth a bullet.