It looks like a whole bunch of pre-ordered Zecoras are being hit with delays. A few people have reported with similiar messages, including a bunch over on MLP Arena. Either she was way more popular than they expected (which I would expect considering the incredibly limited amount at Comic Con and how quickly she was sold out), or the shipment from China ended up getting lost in the Bermuda Triangle, Either way, it looks like she might be a bit more difficult to acquire for the time being.
In other news, some Toys R' Us are still slowly releasing her. Be sure to call beforehand before you head on over to one, but that might be your best bet if you want one in a timely manner!