The defending champion, looking to become the first player to win three tournaments on 10 occasions, was sloppy in a three-set win over Kyle Edmund on Thursday (AEST).
But just 24 hours later, the Spaniard showed why he was for so long tennis' 'King of Clay' as he dominated an opponent that had headed into the contest in promising form having dropped just seven games in wins over Andreas Seppi and Feliciano Lopez.
Zverev will be disappointed with his showing and gifted his opponent too many cheap points, but Nadal's speed and precision was too good for the world number 20.
Nadal was in the ascendancy from the off, typically dominating from the baseline with his trademark stinging forehands.
Zverev was in trouble when a poor serve and volley was followed by a forehand into the net that gifted Nadal the first break, before excellent work at the net quickly brought up a double-break 5-1 advantage.
Nadal served out the opener to love and broke at the first time in the second when Zverev went long with a stooped backhand at the end of a long rally.
The frustration boiled over for Zverev when he was broken again in a lengthy game three and the German was given a court violation warning for smashing his racquet in anger.
Zverev stopped a nine-game rot by holding to make it 4-1, but it proved a brief reprieve as Nadal comfortably completed his progression to the last eight by breaking for the third time in the set.