Each eyes doesn't hold a certain amount of powers.And it was never stated or hinted that izanagi and izanami are performed in a certain eye. As obito stated if you are lucky enough to unlock amaterasu and tsukuyomi you have a chance at unlocking suusano.Suusano is brought about by combining amatersau which represents the "Material World and Light" the antipode to Tsukuyomi which is the Spiritual World. The powers that represents material world gives the spiritual world a form.This form
brought about by the material world and spiritual world form suusano.
Then later down the road this form can be completed through perfect suusano by making its presence completely psychical.
