hi, quick question: when unzipping a file, which dispatchers should I use? IO or Default?

IMHO I would say IO if you are actually putting the unzipped data to disk.

Sounds good. Seems like most of work is just reading/writing file streams. No CPU intensive work to do. I will use IO then.

Yes Input/Output to slower things (disk, network, etc) makes sense then for your use case to me at least.