Edited together from Facebook posts.
On Zecora and the Weather:
Zecora, as far as I have been able to tell is from a nation other than Equestria where Zebras are the dominant species. Her presence was the first sign that Equestria is only a nation on the pony world and not the world itself. Though it may be a Superpower.
The Everfree forest adopts what to us would be natural weather patterns in the like due to the influence of Nightmare Moon, it's implied that it was the seat of her initial rebellion against Celestia and that Nightmare Moon was somehow able to break Celestia's power over it. However that may not be a good thing as the weather always seems to be overcast and gloomy and dangerous aberrations such as Chimeras and Cockatrice are bred there.
Equestria may be the only nation on the Pony world where Celestia holds power over the weather and thus over everything.
That having been said, holy smokes am I a geek.
When asked for my justification that the Pony World might be post Apocalyptic, my response was as follows:
Simple. Mankind screwed up damaged the planet and ruined the environment nearly beyond repair resulting in mutations both dangerous, such as Discord, Dragons, Gorgons and Chimeras dire, and benevolent, such as the ponies who have adapted to a degree where they have a measure of direct control of their environment. The Alicorns are more than likely an artificial offshoot of such designed specifically to keep the specific pony populations in check and discourage them from abusing their direct manipulation of their environment in the same way as the last intelligent species (mankind) abused their indirect manipulation of such.