Hello Mateusz how long is the name of the zip? It is weird that there would be this error unless your site is stored deeper than the default C:\inetpub\wwwroot\KenticoProject if you have it deeper in folders than you can run into this issue for sure since the path will be too long to the temporary files, you could try renaming your zip to a shorter name to see if it resolves the issue.
Also you can extract the zip to a folder with the exact name of the zip ( without the .zip extension ), in the root of this new folder should be the Data folder from the import zip and any other files / folders on that same level within the import. the folder would be something like ~\CMSSiteUtils\Import\NameOfZip
This should help with your issue as it will no longer need to extract the zip to the temporary directory.