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\documentclass{scrartcl}
\usepackage{mathtools}% lädt auch amsmath
\begin{document}
\begin{alignat}{2}
&\Leftrightarrow & \tilde{\mu}_1 &= \frac{\sum_{i=1}^N(1-\gamma_i(\theta))y_i}{\sum_{i=1}^N(1-\gamma_i(\theta))}\\ 
\frac{\partial g(\tilde{\theta})}{\partial \tilde{\mu}_2}=0\quad\qquad 
    &\overset{\clap{analog}}{\underset{\clap{zu 3.13}}}{\Leftrightarrow}} \quad\qquad 
    & \tilde{\mu}_2 &= \frac{\sum_{i=1}^N\gamma_i(\theta)y_i}{\sum_{i=1}^N\gamma_i(\theta)}
\end{alignat}
\end{document}

&\Leftrightarrow \quad & \tilde{\mu}_1 &= \frac{\sum_{i=1}^N(1-\gamma_i(\theta))y_i}{\sum_{i=1}^N(1-\gamma_i(\theta))}\\
\frac{\partial g(\tilde{\theta})}{\partial \tilde{\mu}_2}=0\quad &\overset{\smash{\text{analog}}}{\underset{\smash{\text{zu 3.13}}}{\Leftrightarrow}} \quad & \tilde{\mu}_2 &= \frac{\sum_{i=1}^N\gamma_i(\theta)y_i}{\sum_{i=1}^N\gamma_i(\theta)}