Let $\lambda_1, \lambda_2$ be the values of $\lambda$ for which the points $\left(\frac{5}{2}, 1, \lambda\right)$ and $(-2,0,1)$ are at equal distance from the plane $2 x+3 y-6 z+7=0$. If $\lambda_1>\lambda_2$, then the distance of the point ( $\lambda_1-\lambda_2, \lambda_2, \lambda_1$ ) from the line $\frac{x-5}{1}=\frac{y-1}{2}=\frac{z+7}{2}$ is $\_\_\_\_$