If you have a friend with a working copy of Black Ops 1, ask them to zip their entire zone folder and send it to you. Overwriting your corrupt zone files with known-good ones fixes the error instantly, bypassing Steam verification entirely.
"exe_cannot_find_zone" Call of Duty: Black Ops 1 typically indicates that the game engine is unable to locate critical localized data files or that the installation is incomplete. This error is common for players who have only installed the Multiplayer component without the Singleplayer (Campaign) files, which contain shared "zone" data necessary for both modes. Core Solutions black ops 1 error execannotfindzone hot