Some community-made "Injustice 2" titles found on sites like Internet Archive are actually standalone fighting games built on the M.U.G.E.N engine rather than the official NetherRealm game.
To install modded skins, you typically extract the zip and move the folders to: Steam > steamapps > common > Injustice 2 > DiscContent > DLC . File: Injustice 2.zip ...
If your official game is acting up, instead of downloading random zip files, use the Verify integrity of game files feature on Steam to repair corrupted data. Some community-made "Injustice 2" titles found on sites
Modders frequently bundle re-textures (like "Deadpool" or "Jor-El") into zip files to be placed in the game's DLC folder. instead of downloading random zip files