content zoom issue in firfox browser

I am interested in zooming out a div with 100% height in mozila or firfox browser. The problem I am having, is when I scale the element out it gets a fixed height and no longer extends 100% of the height.

exapmle: iam giving to body tag [enter image description here][1]

also below image attached

enter code here []: https://i.stack.imgur.com/c95Wa.pngtinting