no he is not. if u look at http://www.onemanga.com/Naruto/457/06/ zetzu or wat ever his name is says that danzos no friend and when madara is akatsuki leader.
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When Danzo held Karin hostage, Sasuke used this opportunity and sacrificed Karin by stabbing her with his "Chidori Spear" to get Danzo through the heart. Within his last few minutes of his life, Danzo used his final Jutsu called "Reverse Four Symbol Sealing" in hopes of sealing Madara and Sasuke along with him in his death, but it failed since Sasuke and Madara got away from it in time and Danzo ended up in suicide.
The Konoha Council and Danzo were the ones who told Itachi to kill the Uchiha clan.
behind Danzo's mask is what Danzo absorbed out of Uchiha Shisui.
Madara is not Tobi.
kisame assumed madara was the fourth mizukage , after all fourth mizukage yagura was actually manipulated by madara/tobi ... so you can assume that madara was the real mizukage and yagura was just a puppet ...