> I'm not sure which would be cheaper/faster/better. I believe the program MarcEdit (*) has a batch Z39.50 lookup for a given list of ISBN's. The Evergreen Z39.50 UI is geared toward dealing with one record at a time, so you may have better luck pulling the data with MarcEdit, and then importing into Evergreen.
* - http://people.oregonstate.edu/~reeset/marcedit/html/index.php -- Jason
