Generally before running a file it would be scanned.
I can only go on what the avast help file says about what files are scanned on the scan created/modified files, see image, but to me that would appear to be all files.
I don't think zip/rar files would be scan just because you open it as at that point nothing has been run. When you extract, then you fall into the create/modified scan area, then if you try to run an executable that to would then be scanned 'before' it is allowed to run.
I don't know if an iso would be scanned as it really isn't an executable file more an archive file, but when it is burned to a CD, etc. then the created/modified 'could' come into play again.