The visitors took an early lead in the sixth minute through Raphael Varane, who was at the right place to tap in Toni Kroos’ low cross.
Kroos was once again the provider for the second goal as he played in Lucas Vazquez in the penalty area, and the Spaniard drilled his effort past Zaragoza goalkeeper, Alvaro Raton.
Zaragoza threatened briefly through Shinji Kagawa, who saw his strike from the edge of the box tipped over by Alphonse Areola.
The visitors grabbed another in 72nd minute as Vinícius Júnior found back of the net to make it 3-0.
The Brazilian with a fine run at the Zaragoza defence and played a neat-one two with James Rodriguez, the Colombian then threaded a pass through to the winger, who held his composure to fire a low strike past Raton into the bottom-left corner.
And Benzema stabbed the ball home to complete the rout for the visitors. Los Blancos had their fourth goal of the evening as the Frenchman converted from close range.
Madrid put forward a professional and clinical performance in the final third while being solid at the back yet again.
Zinedine Zidane will be pleased with the standard of display from his boys.