We need a php script running on the same server capable to add images, create a new nextgen gallery, and make a post.
-script detects an uploaded zip file which not yet been posted (script will run by cron job)
-unzips and installs images in a new gallery named the same as zip file. Images have description in a text file. One description for all.
-creates post using data from a text file (post title, category, etc.) adds the [nggaller=ID] tag
Basically creating a post and a gallery from a text file, adding images to a new nextgen gallery entry. As simple as that.