yknow it occurs to me that Zapp Brannigan is less of a parody of Kirk SPECIFICALLY, both in terms of pop culture impact and the actual character, in that while he spoofs the speaking patterns of Kirk's actor, he seems to be SPECIFICALLY a parody of the 'captain space defender of earth' character archetype, taken to its most logical extreme?
There's definitely something to this!
I mean: there are clear Kirk or Kirk-adjacent elements -the speech pattern as you say, the paunch(tho that's more movie-era Kirk), the Star Fleet miniskirt- but there's more than a little of Flash Gordon and the many, MANY Pulp SciFi Space Captains in Brannigan.
I'd also like to add that Groening's work has always been satirical at heart so, while def being done in the language of SciFi and certainly poking fun at certain characters and tropes in the genre, he might have also been hoping to poke holes in all the Hero-Generals and political chickenhawks of that era.
OH WAIT!!!! I also wanted to share this Really Neat Link I Just Found, trying to look up the inspiration for Zapp's uniform. it's to an independent Futurama Wiki called The Infosphere, and it pretty much confirms your suspicions :3
