A mod that is not shown as "compatible" with 1.12.5 still has a great chance - if it isn't too old - to work in 1.12.5. Mod compatibility does not imply that "if it isn't compatible, then it won't work".
The sole fact that they are not up-to-date to the latest version of KSP doesn't mean they won't work with it. Generally, if a mod works in a.b.xx (whatever xx be) they it will also work in a.b.yy (whatever yy be), in other words, if it works for some minor release of some major release then there's no reason for it not to work with any other minor release of the major release.
Now, these two mods do work in 1.12.3. They will work in 1.12.5, or any minor version of 1.12 - actually, it has been tested, and HUDReplacer works in KSP 1.8 and above. Ztheme doesn't have code in it, and only relies on HUDReplacer, therefore it will work if HUDReplacer works - unless new UI elements have been added between whatever version Ztheme's developer is running (1.12.x probably) and 1.12.5, which I really doubt.
