More syntactic constituents

I've talked about syntactic constituents before (here), and recently another difficult regarding them came to my attention via the Famous Dave's web site. On their site you are prompted to "enter either a zip code or select a state". If this were proper VPE (Verb Phrase Ellipsis), I would be expected to (i) enter a zip code or (ii) enter select a state. Since (ii) is ungrammatical, clearly something has gone wrong here. My guess is that this phrasing resulted from a blend of (a) "enter either a zip code or a state" and (b) "either enter a zip code or select a state". Note that with (a) we get (ai) enter a zip code or (aii) enter a state, and with (b) we get (bi) enter a zip code or (bii) select a state. However, as is the request would be parsed as [enter [either [a zip code] or [select a state]]].