Make sure the .zip and .z01 files are in the same folder, and that their names match exactly, except for the extensions.
Also, don’t try to open or extract the .z01 file directly, only open the .zip file using a program like 7-Zip or WinRAR.
If you're still getting an error, try updating 7-Zip or WinRAR to the latest version, that usually fixes most extraction issues.