>>42234531Donkeys IRL are roughly pony sized tho. Zebras are horse sized. Idk, I'm working off the assumption that a long long long long long long time ago there was just normal horses (who could talk) in the MLP world. And their relatives, donkey zebras etc. Then came non-magic ponies as an offshoot of horses like in real life. THEN the Ponies gained magic somehow which led them down the path they're at today. Meanwhile horses went extinct/rare.
I know that's a lot of assuming but that's always how I've figured this world must work, given what we've seen. Zebras really shouldn't be of pony height unless they have pony genes mixed in. If magical, modern ponies came from horses then that means horses existed at some point and it makes sense zebras would have been distant cousins of horses since that's how it is irl.