Fusion of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Ca</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>48</mml:mn></mml:mrow></mml:mmultiscripts><mml:mo>+</mml:mo><mml:mmultiscripts><mml:mi mathvariant="normal">Zr</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>90</mml:mn><mml:mo>,</mml:mo><mml:mn>96</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>above and below the Coulomb barrier

Fusion-evaporation cross sections were measured in the two systems $^{48}\mathrm{Ca}+^{90,96}\mathrm{Zr}$ in an energy range from well below to well above the Coulomb barrier. The sub-barrier fusion of $^{48}\mathrm{Ca}+^{90}\mathrm{Zr}$ is reproduced by coupled-channels calculations including the lowest quadrupole and octupole vibrations of $^{90}\mathrm{Zr}$, and using a Woods-Saxon potential with a standard diffuseness parameter a = 0.68 fm. However, the fusion cross sections are overestimated above the barrier. The low-energy slope of the excitation function for $^{48}\mathrm{Ca}+^{96}\mathrm{Zr}$ is steeper. This implies a larger diffuseness parameter a = 0.85 fm. Fusion cross sections are well fit in the whole energy range, and the effect of the strong octupole vibration in $^{96}\mathrm{Zr}$ is predominant. The extracted fusion barrier distributions are reasonably well reproduced by calculations for both systems. A comparison with previous data for $^{40}\mathrm{Ca}+^{90,96}\mathrm{Zr}$ is made in an attempt to clarify the role of transfer couplings in sub-barrier fusion.