A small guide to not have texture overrides:
1.As they are custom textures, you can easily rename your textures as zombie_helmet_diffuse.dds, zombie_footman_diffuse.dds... Or even as zombie.dds, helmet.dds, it doesn't matter if they are not the same name as the _Normal or _ORM files.
Now, replace the _Diffuse files for your own texture names, like in this image:
And voilà, there you have it. Now you can have footmen AND zombie footmen in the same game.