os.symlink needs the target_is_directory argument on Windows. Maybe extract() can search for the link target in namelist() to determine if it's a directory (i.e. ends in "/"). Note that the flag gets set automatically if the target exists, so this is only a problem when a link is extracted before the target.

Also, I think it should fall back on creating a regular file if os.symlink raises OSError. On Windows this occurs if the user doesn't have SeCreateSymbolicLinkPrivilege. os.symlink raises a plain OSError in this case; no errno/winerror is set. (I don't know why it doesn't simply call CreateSymbolicLink and raise an exception for the last error, which would be ERROR_PRIVILEGE_NOT_HELD.)