If the shortest distance between the lines (x-4)/1=(y+1)/2=z/-3 and (x-λ)/2=(y+1)/4=(z-2)/-5 is 6/(√ 5), then the sum of all possible values of λ is:

If the shortest distance between the lines $\displaystyle \frac{x-4}{1}=\frac{y+1}{2}=\frac{z}{-3}$ and $\displaystyle \frac{x-\lambda}{2}=\frac{y+1}{4}=\frac{z-2}{-5}$ is $\displaystyle \frac{6}{\sqrt{5}}$, then the sum of all possible values of $\displaystyle \lambda$ is :