You can see a picture on her flank. Without any other zebra appearing in the show (I don't follow comics) it's hard to tell more than that. And in the episode under discussion, Twilight (who knows Zercora pretty well) seems fairly certain that only ponies can get cutie marks
After all this time, I still find it crazy how the Friendship is Forever clip show specials have been canned at literally the last second.
Derpibooru costs over $25 a day to operate - help support us financially!