Here's my opinion... since my fades are doing various degrees of work/flexing... and actually helping halt the bend from entering the handle... I only use wood of such species and quality that I would trust in the bow's limbs... In other words, if I wouldn't use it as the belly lam of a tri-lam, I wouldn't use it in the dips/fades either. That way, I have no doubts or concerns about it.
Personally, no, I would not use zebrawood in the handle/dips of a tri-lam. I have stacks and stacks of exotic and domestic hardwoods in my shop and almost invariably use osage for such applications.