Alcaraz targeting 'best level' to beat Zverev at Australian Open
The second seed - seen as the biggest threat to defending champion Novak Djokovic - did not face a single break point in a dominant performance, rolling over his opponent 6-4, 6-4, 6-0 in one hour 49 minutes.
The Spaniard, who chose not to play any competitive tennis in the build-up to the first Grand Slam of the year, said he "did everything perfectly" at Rod Laver Arena.
But admitted he would have to find another gear against sixth seed Zverev, who won their most recent meeting at the ATP Finals to lead their head-to-head 4-3.
"He is a really great player," said the 20-year-old. "He has beaten great guys here in this tournament.
"Obviously I love playing against him. It's always tough battles. I have to play my best level. He pushes me to play 100 per cent every time.
"The last time we faced each other, I lost so I have to be focused on that. I have to improve my level from that match."
Zverev, who beat British 19th seed Cameron Norrie to progress, lost to Alcaraz in the quarter-finals of last year's US Open, but he played down the parallels and said he had fuel in the tank, predicting a "very fun, entertaining match".
"I'm tired, for sure, because I played 7-6 in the fifth set again two times out of the last three matches, but I'm not dead," said the 26-year-old German.
"I'm not completely exhausted. I'm not in the same physical state I was in the US Open. I expect it to be very different, to be honest."
Alcaraz, making his first appearance in the last 16 at Melbourne Park, was quickly into his stride, breaking in the third game.
The second set went with serve until the seventh game, when Alcaraz broke again, which proved enough for a two-set lead.
The third set became a procession as the Spaniard stepped up a gear - a deft drop shot set up match point and a thunderous serve sealed the deal.
Alcaraz has yet to be fully tested but has shown glimpses of his best form in Melbourne.
In Monday's match he won 83 percent of first-serve points, took advantage of five of his nine break points and hammered 43 winners.
The Australian Open is doubling up as a shootout for the number one spot and defending champion Djokovic has already laid down a marker, dropping just three games in his fourth-round match on Sunday.
