Hi all !!
I don't know if this is the right method but i have good issue with that, so...
I use Winrar to make it, never winzip !!
First open your map with winrar, extract all the files include in a folder call what you want, in this case "pack".
Extract all your maps like this in the same folder.
After, you select all the files and with a right click mouse, select in the menu "add to archive" or something like it.
In the windows of winrar, select the option "zip" and verify that the compression is at "normal".
Ok, and you have your pack. rename the extension .zip to .iwd and it's done.
Generally, i use to take soundaliase folder, and put it in the fs_game server folder. it's gain time.
I hope you can understand my poor english !
Bye