There's no exact linearization that I've ever heard of. You can do a piecewise linear approximation, or you can do a McCormick relaxation (which is again an approximation). The latter requires both upper and lower bounds on both Y and Z. If Z is binary (or at least integer) then you can do an exact linearization, at the cost of a size increase in the model (if Z is general integer). answered 24 Jan '16, 16:21 Paul Rubin ♦♦ thank you very much
(25 Jan '16, 05:21)
saeed

Yes, pwl and McCormick are the first approximations/relaxations to try. Here are a few useful resources for more info on the latter.
answered 02 Feb '16, 20:54 Ed Klotz 
Any hints on what Z is or shall we just kinda guess?
No, there isnot any condition on Z but Z>=0
Let V=Z*Y, then \(X\geq V\).