Both downloads failed. The Gdrive died immediately. Mega failed by putting me in a loop after a supposed download while the zip file wasn't downloaded.
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When downloading from MEGA, install their (mobile/desktop) app, then when clicking a MEGA link, choose [Download with app] on the webpage you're sent to (dropdown menu on the right side of the green [Download] button), and you only have to be patient from then on, as the app will resume the download automatically once the waiting period for a new transfer quota is over. If using MEGA's app, you can be certain downloads from MEGA will be completed. And you know the file is always available*, unlike some other filesharing services
*: Of course it won't be available if the uploader has deleted it, or their account, or they for some reason have been banned, but as long as the file is on MEGA's servers, you can always access it, unlike some filesharing services that doesn't even allow you to access the linked file based on their (unstated) transfer quotas.