Vol 1: Select pictures and then create album
Vol 2: Create dynamic album or open an existing one and then select pictures for it
Vol 3: add more pictures into dynamic album in frontend
Today we can create dynamic albums only from search results. Such additional feature - album creation from selected pictures would be really user-friendly improvement of Zp
Zenphoto has no mechanism for grouping "items" other than the search capability. While the above might be convienent, there are other ways to accomplish this, notably by tagging the images with the "group" they belong to.
There is already a ticket for "mass edit" of tagging. Also a difficult proposition since it would most likely involve creating a list of all the images on a site--probably a killer for large sites.
At any rate, unless a feature ticket is created I am sure this request will get forgotten as it is not possible to do "over night".