It's interesting to read that you didn't think that's Ganon. That zombie is at the very least a male Gerudo. Hair and jewelry match to my newbie eyes. For those more keen, apparently the symbols coming out of the green vortex thing are Gerudo language.
Ganon is perhaps the most infamous male Gerudo.
Also perhaps people are looking into it too much but people are saying this zombie seems to call back to Twilight Princess' Ganon. I never beat the game (I personally was able to figure out how to get to the last level...) so I never faced Ganon there. But yeah, if Calamity Ganon is the manifestation of a real, physical Ganon, it changes the outlook of the first game. There's also a distinct possibility that Nintendo is doing more timeline things, for better or for worse.