DR Elmore - the Offenbach piece played by the zookeeper's wife was "Go, Go, Go to Crete" from La Belle Helene.
In The Zookeeper's Wife, Diane Ackerman spends several pages on Offenbach - pp. 174-177. These reference are to the Large Print edition, the only copy available here today. I suppose the day may come when I'll appreciate large type, but for now I couldn't read a whole book in that format.