Mini-z and mini-x have different wheel bases and widths so it would take a great deal of custom work to the body to make it fit and then it wouldn't look too good once it was done.
A much better solution would be to use a 1/25 scale model body. Another option is to use a 1/24 scale slot car body. They are light, easy to mount, and don't require too much cutting to fit the mini-x wheel base.