\documentclass{article} \usepackage{amsmath,amssymb,nopageno} \usepackage[all]{xy} \DeclareMathOperator{\id}{id} \begin{document}  \begin{equation*}   \[email protected]@R+2em{   & {H \otimes H} \ar[rr]^{S \otimes \id} & & {H \otimes H} \ar[dr]^{\nabla} & \\   {H} \ar[ur]^{\Delta} \ar[dr]_{\Delta} \ar[rr]^{\varepsilon} & & {K} \ar[rr]^{\eta} & & {H} \\   & {H \otimes H} \ar[rr]_{\id \otimes S} & & {H \otimes H} \ar[ur]_{\nabla} &   }  \end{equation*} \end{document} 

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