samehada gets hurt by fire style jutsu madara wont just stand there and let kisame attack him if all else fails madara uchia would fight kisame up close and he would be able to dodge kisames attacks because he has the sharingan and would be able to read all of kisames attacks and would be able to predict kisame's next attack and then use that to his advantage to beat kisame.madara throws a fire ball, samehada cuts it in two, kisame uses Daikodan no jutsu (Sucks up ninjutsu and makes it stronger)
counter that.
Madara would win. kisam is wounereble to genjutsu.
and if madara where to easily separate samehada from kisame then kisame is vulnerable to genjutsu