I usually start pairing my birds ready for breeding in March and end around September/October depending on weather conditions. Although Zebra finches will breed all year round, I find it better to give the birds a good rest over the winter period. I have also found it beneficial to give the birds a rest between clutches.
Both birds do their fair share of incubation and normally start to sit the eggs after the third or fourth egg has been laid.
incubation periods last between 12 - 14 days dependant on weather conditions.
Fit closed ring between 8 - 10 days old.
Young should fledge (leave the nest) around 21 days old.
At 4 weeks old they should start to eat on their own.
At 5-6 weeks old their adult colors will start to develop, along with the beak changing colour.
You should also consider moving the young to their own cage at 5-6 weeks old or when you notice that they are feeding themselves. The longer you leave them with the adult birds the more risk that the parents will start plucking them and chasing them around the cage. This is usually a sign that the adults are ready to produce their next clutch.