Within the same genus would be a possibility but even then, the babies might not develop. Try to keep the cross breeding as closely related as possible -if you even get them to mate across species - but otherwise I wouldn't because it's likely to lead to undeveloped eggs. DNA tells the eggs how to develop and produce chameleons and when you mix things up (perhaps even with different amounts of chromosomes) there may be strangelings that don't survive - even if they make it thru gestation.