Great to see that the ability to export modpacks has been added.
The problem is that the exported ZIP file includes every mod which causes the export file to be massive. This makes makes transferring the export file to friend's computers time consuming.
I believe Twitch would include all the mod IDs in the manifest.json file when exporting a modpack. When another computer imports the export file, the launcher would re-download all the mods based on this manifest.json file. This meant that the mods didn't need to be exported within the ZIP file which made the export file very small (Typically under 1MB). For comparison, most modpacks exported through the new CurseForge launcher are currently exporting at 200MB+.
TL;DR Please exclude the mod files from the compressed export file and allow the launcher to re-download the mods during the import process to make the export file smaller.