What kind of organization was ZOWIE?

Sure, IN LIKE FLINT was all good, quasi-comedic, superagent fiction fun. Still, the movie takes place in the real United States. So it was never explained, what kind of government or military agency was ZOWIE? The commissioned officers' dress A uniforms were straight out of the real American Army. Those dress A uniforms remained essentially unchanged until 2010 when the U.S. Army reassigned its existing, special-occasion Mess 'blues' uniform to replace the green A dress uniform.

The enlisted men wore khaki uniforms straight out of the late 1950s to early 60s. While the green khaki was more prevalent, the khaki color version existed as well and looked dressier and more suited to peacetime. So basically the movie director adapted the U.S. Army to fill a domestic, para-military organization, whose charter and purpose were never explained in the movie.