TY the Tasmanian Tiger

Much like Zone A, simply progress through the 9 missions in this zone, and the reach the boss battle. This boss battle, as the achievement suggests, is against Sly. You will be on the back of a boar and he will be riding a mechanical creature. Simply continue to chase him, being mindful not to get hit by his attacks, and eventually he will lose health as he hits items throughout the chase. This boss fight is very easy, and should be beatable on your first attempt.