Green’s Dictionary of Slang

(US black) as applied to clothes, of an over-exaggerated style or cut .

1944		Cab Calloway New Hepsters Dict. in Calloway (1976) 261: zoot (adj.): overexaggerated as applied to clothes.
1947		N. Algren Neon Wilderness (1986) 153: It [i.e. an outfit] was loud green checks and a zoot cap so wide it flopped over his ears.
1954		J. Thompson Swell-Looking Babe 40: Two men with zoot coats and snapbrimmed hats.
1954		K. Vonnegut ‘Ambitious Sophomore’ in Bagombo Snuff Box (1999) 127: He buttoned the great brass buttons and fluffed up the gold braid cascading from the epaulets [...] ‘Zoot!’ exclaimed the delivery boy. ‘Man, I mean zoot!’.
1974		(con. late 1940s) E. Thompson Tattoo (1977) 503: He took out a gold penknife on his zoot chain and twirled it.
1986		B. Geldof Is That It? 41: I wore zoot shoes, square toed.