Behind a 4.0L - definitely. There will probably be some work involved with getting the t-case, shifter, and linkage connected, but check out http://stu-offroad.com/engine/aw-4/aw-4-1.htm to see how to get one into a TJ. Check out www.nagca.com and www.mallcrawlin.com to see whether it's been done in a ZJ before.
There are issues with the TCU when installing an AW-4 into a ZJ if it wasnt an early one that had it originally. It will bolt up but shifting will be done manually with some work is my understanding.
I'm assuming you have issues with the POS 42re?
Believe it or not, there is actually a good thread at www.jeepsunlimited.com on this topic.