request and send files to external

currently our sharepoint admin center, we allow certain external domain (parent and other subsidiary company only)

sharepoint external sharing is set 'new and existing guest' so files and folders that need to share with parent and other subsidiary are done at sharepoint.

onedrive external sharing is set 'only people in your organisation' because we dont want user's onedrive to share with external.

however we have this scenarios which is sending huge file size to external company and request huge files size to external company who are not our parent and subsidiary.

anyone has any idea or other ways to send huge file size to external company and request huge files size to external company who are not our parent and subsidiary?? thanks