zDefine behaves exactly like Define, except that it does not add the definition to computeLib.the_compset. Consequently the definition is not used by bossLib.EVAL when evaluating expressions.
FAILURE
zDefine and Define succeed and fail in the same way.
zDefine is helpful when users wish to derive and use their own efficient evaluation theorems, which can be added using computeLib.add_funs or computeLib.add_persistent_funs.