ezpm script won't work if you try to import a big package (in my case, I tested it with 11Gb) using the following command

php ezpublish/console ezpublish:legacy:script --siteaccess=my_sa ezpm.php import my_package-1.0-1.ezpkg

I checked ezpackage.php and it seems the error happens when it loads the file into a new DOMDocument.
According to what I searched in the Web, this kind of object may not work properly if it exceeds the available memory (it's a really large package, with a really large XML File).

That said, it's important to add a known limitation with the maximum allowed size for a package to be imported with ezpm. Also, it would be important to have this warn added to the package creation page.