ooooh the manticore looks so cool. Also I pricture zebras to be more like the original earth ponies: still very in tune with the natural magic of the land. As such they have some sway/manipulation over it and can read it well. Hence the potion making which was unfamiliar to Twilight. I don't imagine them able to do arcane style magic like unicorns, but more tap into the inate wild magic around them. We've basically seen that previous generations of earth ponies had to be aware of it: given how Granny Smith and her parents had to handle the zap apples. I think in general causing the plants to grow in this world is knowing how to pay attention to that kind of magic, and I wouldn't be surprised if earth ponies were the only ones who could truly sense it.



Anyway we all have our own in-head explinations. Either way this looks amazing!