User blog comment:Kaido King of the Beasts/The Nature of the Zou Arc/@comment-972068-20151208090234/@comment-24769684-20151210023700

Punk Hazard was when Luffy and Law formed an alliance to take down Kaido. They completed phase 1 of their plan there

Dressrosa was phase 2 of the plan. However, Law threw a curveball when he revealed that his real motive was to bring down Doflamingo's Empire and gain revenge by having Kaido kill the Shichibukai. However, things didn't go as planned as Law was forced to help take down Doflamingo himself and put him and Luffy in Kaido's spotlight

The main purpose of Zou, then, is for Law to regroup with his crew and further the samurais journey as they headed off into the unknown. The thing is, though, Law has kept rather mum about his plans after the battle with Doflamingo. I guess we'll find out this arc whether he plans to continue the fight he didn't want in the first place or if he'll do something else