Let $${z_1}$$ and $${z_2}$$ be two non-real complex cube roots of unity and $${\left| {z - {z_1}} \right|^2} + {\left| {z - {z_2}} \right|^2} = \lambda $$ be the equation of a circle with $${z_1},{z_2}$$ as ends of a diameter then the value of $$\lambda $$ is