Image imported from derpibooru
Original Description:

The world of Generation Four collides with the ponies of Generation Five as Cloudsdale threatens to crash into Zephyr Heights and cause an eternal winter! Only Princess Zipp and her Mane 6 can stop the kingdom from falling (literally)!
After the torrential winds and snow force the Pegasi to seek refuge in the castle, our heroes split up to solve this raging mystery! As Princess Zipp and the other flyers push forward to find the cause of the storm, the grounded ponies discover an airborne relic of the past in need of a little rescue!

As their discoveries push our characters closer together, they also trigger more questions about the past… and the ponies’ futures!