It seemed better to breed green-yellow hybrid with green-yellow hybrid, rather than pure green and pure yellow.
Island 1 - 1st try Daisy (green yellow) Jasmine (green yellow).
Island 2 - greenstone (green) and neo air (yellow), multi fails, no success.
Island 3 - eventually successful with sunblaze (green yellow) Franken (green yellow) after multi fails 2 druids, 2 cacti, 1 fairy, 1 lochness, a few other 4-hrs commons. I used both boost and gold to speed breed and speed hatch.