The magnetoresistance (MR) and the saturation resistivity (ρ_s) are studied versus the Cu deposition pressure (P_Cu) at room temperature, in [Co98Zr2 (25Å)/Cu (t_Cu) /Co (25Å)] magnetic sandwiches prepared by RF diode sputtering. Results of low angle X-Ray Diffraction patterns have been proved the importante interfacial degradation observed in (CoZr/Cu) multilayers, compared to the usual (Co/Cu) structures. The highest value of transverse MR is obtained along the easy axis, and the MR curve saturates in a small magnetic field of 100 Oe at room temperature. Which leads to an interesting increase in MR sensitivity about 2%/Oe. The main features of the magnetoresistive properties evolution with Cu deposition pressure are: The maximum of MR increases and moves towards larger Cu thicknesses (t_Cu) for increasing P_Cu. The saturation resistivity ρs decreases with increasing t_Cu while it increases versus P_Cu. The satisfactory agreement between our experimental results and calculated ones in the framework of the Johnson-Camley semi-classical model, allows us to interpret the MR and ρ_s behavior as a result of a reinforcement of the disordered phase ″CoZrCu″ inside the mixed zone whose thickness t_mx increases with P_Cu .