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Zverev, who also downed Blockx in the semi-finals at the Madrid Open, repeated the trick with a comfortable 6-1 6-4 triumph in one hour and 13 minutes. 

The two-time Italian Open champion set the tone for his victory in the second game of the opening set as he got the better of Blockx's serve to race into an early 3-0 lead. 

And though Blockx got himself on the board, it was too little, too late for the Belgian, as Zverev clinched the set at the second time of asking to edge closer to the next round.

The German's dominance continued in the second set, with a break in the first game setting him on his way, though he did squander two more break points soon after. 

For all of Blockx's efforts, Zverev showcased his experience and saw out the match with ease, sealing his progression with a blistering, unreturnable serve.

"I was much better than I was two days ago," said Zverev, who beat Daniel Altmaier in his Rome opener.

"I think it was difficult to play pretty tennis from the baseline today because the conditions were not easy, it was very windy. But overall, I am very happy."

Zverev will be joined in the next round by Casper Ruud, who also won in straight sets against 11th seed Jiri Lehecka.

Ruud emerged a 6-3 6-4 victor in one hour and 19 minutes, teeing up a clash with either Lorenzo Musetti or Francisco Cerundolo for a place in the quarter-finals.