Mirai-hen will premiere on 11 July, while Zetsubou-hen will be making its premiere on 14 July, and this really shows that we are getting two Danganronpa episodes in the same week!
While Mirai-hen is a completely original story, featuring the return of the original Danganronpa survivors, together with several new characters, Zetsubou-hen will be based on the second Danganronpa game.
You can check out the story for both arcs through this link.