I have a flight with zebras and Java Rice birds in one side and Shafttails and Lavenders in the other side. A friend just gave me a Gould male who lost his mate. Can he go into the flight? If so, which group is preferred?
Most often zebras and javas can be kept with Gouldians, but a lot depends on their individual temperments. I would watch them all for quite a while before I felt they were safe together especially if the Gouldian is to stay a lone Gouldian. I don't know anything about shafttails. I do believe that Lavenders are compatible, but not when they are breeding. I would try to find a second Gouldian, the same sex is fine, just a companion of his own kind and I would go with the zebras and the javas.
Good luck, Jeanie