Hi. please see an image:

i wrote:

Code:

\begin{tikzpicture}[auto,>=stealth']
\node (N) {$\llap{$e:{}$}N$};
\node[right=of N] (L) {$L$};
\node[right=of L] (Q) {$Q$};
\node[below=of N] (N1) {$\llap{$e_2:{}$}N \oplus N_2$};
\node[below=of L] (L2) {$(N_2,\varphi _{2}\pi)\oplus L$};
\node[below=of Q] (Q1) {$Q$};
\draw[->] (N) -- node[swap] {$i$} (N1);
\draw[->] (L) -- node[swap] {$\lambda$} (L2);
\draw[->] (Q) -- node[swap] {$$} (Q1);
\draw[to reversed->] (N) -- node {$\chi$} (L);
\draw[->>] (L) -- node {$\pi$} (Q);
\draw[to reversed->] (N1) -- node {$\chi_2$} (L2);
\draw[->>] (L2) -- node {$\pi_2$} (Q1);
\path[use as bounding box] (-1.5,0) rectangle (0,0);
\end{tikzpicture}

how can I do for soleving this problem ?please right answer.

thanks