The file manager would ask you to pick (using the Android UI, via SAF) the directory where you had downloaded the zip, then everything would work the same.
Alternatively, the app can register itself as opener of zip files, then it could extract them freely to its own private directory (without asking for permissions) and let you list and upload them.
This is all a load of crappy workarounds leading to a convoluted and cumbersome user experience. From a usability perspective, I would not consider such a behavior a solution.
The alternative is malware having free reign over the entire filesystem. This is a real problem which is happening today. With your all-or-nothing solution the user has no ability to limit what files an app can access, which is totally unacceptable.
Apps need my permission to access external storage even today. I don't see how a convoluted UI helps here.
Although it may not be international (I think intentions are good), this change will devalue internal device storage to such an extent that people will see themselves forced to store even more data in cloud services of dubious reputation. Technically, they don't have to, but it will likely be easier for the masses.
> Apps need my permission to access external storage even today. I don't see how a convoluted UI helps here.
Consumers tend to just click past permission prompts, hence granting malware permission to everything. Power users can take care of themselves, of course, but most consumers don't have the technical knowledge to safely deal with this kind of permission prompt.