Green’s Dictionary of Slang

zippered adj.

drunk.

1949		H. Miller Sexus (1969) 143: Underfoot it was slimy and slippery, as if an army of zippered seals had been weaving it back and forth to the washroom all day long.
1993		R. Shell Iced 114: I was already zippered by the time I was to meet Maggie.