\[\frac{z_{1}}{z_{2}}=\frac{z_{1}\overline{z}_{2}}{{\left|z_{2}\right|}^{2}}=%
\frac{x_{1}x_{2}+y_{1}y_{2}+\mathrm{i}(x_{2}y_{1}-x_{1}y_{2})}{x_{2}^{2}+y_{2}%
^{2}},\]