Help Breeding Zebra Finches

Make sure you have plenty of room. Your cage is going to get crowded.
Trade some young birds to promote genetic variety.
A calcium source and lots of good food should help divert his attention. Don't rush the reintroduction. She has her own agenda until she notices that he is really cute and then it will start all over again.

When I had my zebras, I went to this site a lot for advice. They were very nice and very helpful.
http://www.zebrafinch-society.org/ Good luck!

It may be that the female is still young and isn't into the nest/egg frame of mind yet. I would remove the ivy from the cage as it may be poisonous to them.