Hmm… after doing a little investigating, I honestly can’t find anything bad to say about this OC. His design is okay, his bio page actually focuses on his own personal traits (which don’t make him out to be overpowered) and not his relationships with other ponies, and his creator seems like a reasonable sort.
 
And most importantly, it doesn’t seem like he has some sort of bullshit backstory that retcons Twilight’s life in order to shoehorn him in as her childhood crush/destined lover.
 
The worst one could say is that he’s pretty much an expy of Flash Sentry (though ironically, Zephyr seems to be a more complete character). There are other Twi-shipped OCs out there that are much more deserving of ire. Believe me, I’ve seen them.

Personally I don’t hate the guy or his OC, I could honestly care less what people fantasize about or commission art of. What I don’t get is why anyone would commission art of their OC being shipped with any given pony? I’ve always thought that if you like the idea of having a relationship with a certain pony then why not commission art of the real you with that pony? I can’t help but think that would be way more honest and meaningful than commissioning art of some imaginary character you made up with said pony, and yet it’s pretty rare to see human + pony shipping art. It seems like the vast majority of shipping art you see is OC + pony, and I’ve never quite been able to wrap my head around why that is. I’ve speculated that it might be due to people feeling personal discomfort over the idea of an interspecies relationship—even if their heart tells them they want it—or fear of judgment from others for expressing their feelings through art, but that’s all just speculation and I’ve never actually asked anyone why they choose to commission art of their OC being shipped with a pony rather than the real human them.
 
Hmm… ya know what? Lets find out! The question has been asked on Zephyr’s DA page http://zephyr093.deviantart.com =)

@VermiIIion  
I think it’s because he’s a wish fulfillment OC. The owner most likely has fantasies of being Twilight’s boyfriend/husband. To my knowledge, that’s the main reason why people ship their OCs with canon characters; it’s their fantasy.

I wonder why everyone hates this OC. I mean, at least it isn’t Flash.
 
Well, the coat could be lighter than the blue streaks in the hair, and the hooves should be darker or lighter than the coat, not gold.