Hello, I'm new here. Instead of asking a question like most first posters, I'll give a tip.
Out of the app list, the most interesting application for my own part is the FTP server. For those who have troubles finding the IP address...
1) It's at the bottom of the screen, obviously.
2) But more conveniently, on the average commercial wlan router you can just type either nintendods or nintendods.lan instead of the IP address. This is because there's a host name assigned via DHCP. I don't know whether there's some collission detection if several DS's are connected to the same router.
As for the question about zip file: It may be different for different models, but my M3Real (Manager 2.6) can not handle zip files. Fir those using the ftp server, you can save a file as a a gzip stream, and decompress it at the other end, but that's over the top for most users probably.