transform into weierstrass-form

First change $y=2y'$ and $x=x'$. That will leave the model in the form $$y'^2 = (x'-e_1)(x'-e_2)(x'-e_3),$$ after cancelling $4$'s on both sides. Now expand the polynomial, in $x'$, so that you have $$y'^2 = x'^3+Ax'^2+Bx'+C.$$ Finally, a change of the form $x' = X-A/3$ and $y'=Y$ gets rid of the $X^2$ term, and leaves $$Y^2 = X^3+DX+E.$$