The documentation site for foreman have width in pixels rather then precentage for the TOC, having it override text when zooming
The site https://theforeman.org/manuals/ uses a fixed size for the toc div (263px).
When zooming the text, it overrides the content itself (div #doc).
I'ved attached a screenshot that display the issue itself.
I think that by moving the size of the toc to percentage, it will solve the issue.