Let $𝒞$ be a triangulated category and $𝒳$ be a cluster tilting subcategory of $𝒞$. Koenig and Zhu showed that the quotient category $𝒞/𝒳$ is Gorenstein of Gorenstein dimension at most one. But this is not always true when $𝒞$ becomes an exact category. The notion of an extriangulated category was introduced by Nakaoka and Palu as a simultaneous generalization of exact categories and triangulated categories. Now let $𝒞$ be an extriangulated category with enough projectives and enough injectives, and $𝒳$ a cluster...