User blog comment:Sky-Dragoon-Twilight/Weisslogia and Skiadrum, Alive or Dead?/@comment-25600633-20141211153653

About the second evidence, if you read Chapter 303 + watched Episode 176, you see that Acnologia killed Zirconis and many other dragons following the Dragon Civil War while he was a Dragon Slayer himself, and before he turned into a dragon.