Cruz will not be slicing up Trump, or vice versa, they will both go after little Jebbie who needs to be drummed out of the race early.
Cruz can take Bush at any time and he knows it. But take out Bush now and his support goes to Christie or Graham or some other establishment suit. What he needs to do is get all the fringe candidates like Trump and Perry and Carson out of the way so that he can consolidate conservative support behind him. In a heads up race, mano y mano, Bush vs. Cruz then Bush loses. In a three or four way race with Bush and Walker and Trump and Cruz then Bush wins. Cruz is bright enough to know that.