What zip implementation are you using? Occasionally perfectly correct zip files are produced that the zlib java library has trouble reading for whatever reason. I doubt this problem is a fault of either you or the FTB launcher.
You may however want to try using different software to create your zip files in the hopes it will produce one that can be read properly by this library.
I'd really like to play the latest version of your pack.
This has been an on going issue since I posted version 0.0.10 several weeks back. I have recently received word from the admin staff that they have or will repost version 0.0.11 as version 0.0.12 and see if that fixes the issue.
On the other hand I am quickly trying to catch up from the holiday break in order to get the next version pushed out. I will go ahead and try using a different program to create the zip files and see if they are more compatible with the FTB launcher.
Thank you,
OneWolfe-