I have a pair of zebra finches also, and they are not really fond of fruit. Usually if you put something strange in their cage they will be scared of it. You can try giving the female a special blend of food made especially for birds laying eggs. I also bred my zebras, after about a 5 or 6 times trying before it finally worked and they lived. The ones before kept dying. What I would recommend after they hatch is to separate the males and females becuase they will fight. I orginally had 6 birds, 4 males and 2 females, and the males all fought, they fought so much that they killed eachother. But, if you do have a big aivary it is not necessary to separate them. They can also breed very quickly if you do not separate them soon enough. You can keep them with their parents until they are adults. Good Luck!