Adding contact form popup to main menu

Hi,

How to add a contact popup form to main menu?

Im using contact form 7 plus Easy FancyBox to display the forms in pop up windows in GeneratePress,
but I'm not able to make it work properly when the form is launched from a Menu item: either the popup opens a new window with the form and the whole web in it rather than only the form, or it goes to another page or directly nothing happens)

The code I'm using to display the forms is:

 <a href="#contact_form_pop" class="fancybox">Contact Us</a>
<div style="display:none" class="fancybox-hidden">
<div id="contact_form_pop">
        [contact form shortcode here]</div>
</div>

and it works great but I'm not able to add this to a Menu element.
I've tried with shortcodes in menus but the thing is I cannot add html to menu elements ...

could you help me how to do this ?