

No, is not the phone’s CPU. I guarantee you that can process several gigabytes a second.
It’s the overhead of all that handshaking and confirmation coming over USB, and having to be verified with the sometimes slow phone storage chips or worse on a microSD.
It’s IO overhead and waiting all over the place, not a CPU bottleneck.





Not zipped to a flash drive. Zipped and sent over the same USB cable as sending the bunch of files.
The actual transfer bandwidth attained does rely a ton on what connection speed gets negotiated. The overhead of how at least Windows deals with USB is very noticeable at lower speeds. 3.1 or less and I can guarantee you the zip option might start looking like a valid choice.
Of course if you get 3.2gen2+ speeds negotiated, it’s going to be ‘fast enough’ either way assuming the devices can deliver on read/write…