How to add an extra tag to the default images tag in Tinymce

In Tinymce i want to insert the default <img ... > tag into another extra tag to centralized images and add extra class for create zoomable images in my content .

By default Tinymce creates the following html code when add new image :

<p> <img ... > </p>

What I want and need is something like this :

<div class='zoomable content-img'> <img ... > </div>

How can I implement this in Tinymce ?