Moving away from cards.txt

[frwololo]

I don't think performance would be better when zipped.

It is. Most of the file I/O time is spent creating the file descriptor, especially on such small files. Less files == less time spent. One zip file = one file VS 4000 files.
Again, this is probably not such a big problem on modern computers (but a major difference on - yeah I know, always the same example - the PSP specs, which is 333MhZ and 24MB of Ram).