The first, who turned up to speak to TDs behind closed doors, wore a suit with all of the sartorial awkwardness we’ve been accustomed to seeing.
The second emerged via a quick costume change into his more familiar grey sweater-shirt, ready to be mobbed by selfie-seeking workers at Facebook’s expanding Dublin headquarters.
But both Mark I and Mark II had pointed messages to deliver to Dublin policy-makers and, by extension, the rest of Europe.
Flanked by ex-Liberal Democrat leader Nick Clegg (now one of Facebook’s top advisers), ‘Zuck’ laid out a few home truths to would-be regulators and watchdogs.
Echoing some of what he had written in ‘The Sunday Independent’ and ‘Washington Post’ at the weekend, Mr Zuckerberg warned that Facebook alone couldn’t decide what kind of “content” is harmful or not.
Instead, governments and regulators need to start being a little clearer as to what they mean when they say that Facebook “should do something”, he said.
He had a similar line on the issue of political interference, admitting to TDs that Russia would likely again try to disrupt elections and that Facebook may sometimes need help from local authorities in dealing with it.
And on the matter of privacy, he repeated he wants European-style levels adopted in other parts of the world.
Basically, his message to decision-makers in Facebook’s European base was: stop expecting us to decide everything ourselves, start creating and enforcing new laws on the stuff you complain about.
Mr Zuckerberg was far more forthcoming with TDs than he was with local media, with whom he restricted his comments.
He told TDs that he may appear before the Oireachtas in front of a cross-parliamentary committee to answer detailed questions in November.
This may turn out to be significant: he has repeatedly declined summonses to appear at Westminster. (He is also known to believe that testimony appearances before legislatures can descend into ill-informed circuses, as witnessed when he turned up at the US Houses of Congress.)
Mr Zuckerberg also candidly admitted that reclassifying 1.5 billion Facebook users as non-EU data subjects on the eve of the GDPR data privacy law was not a good look. Facebook did it, he told the TDs, for technical and “practical” reasons.
And the 34-year-old Facebook boss said that his company will not drop its appeal to the UK information commissioner’s £500,000 (€586,000) fine over the Cambridge Analytica data scandal. He is said to have told the TDs he does not believe the company deserved the fine.
Mr Zuckerberg was meeting parliamentary TDs Eamon Ryan, James Lawless and Hildegarde Naughton in Dublin as part of an outreach exercise with an international ‘Grand Committee’, made up of politicians from the UK, Ireland, Canada, Australia and Argentina.
The Facebook boss also toured the company’s facilities in Dublin, which currently employs more than 4,000 people and is set to add another 1,000 this year.
Mr Zuckerberg also met journalists, but restricted his answers to pre-prepared remarks.
However, he was willing to put to bed one accusation frequently levelled at him. Asked whether Facebook or Instagram records voice conversations through smartphones to inform targeted ads, he said: “Absolutely not.”
However, he again warned about Apple’s “competing vision” for the internet, making a thinly veiled reference to the iPhone company when referring to data “stored” in countries like China.
“GDPR is as important for what it doesn’t do, which is require companies to localise data and store systems data in a given country,” he said, referring to Apple’s compromise with Chinese authorities, where it stores data in servers located in that country. Facebook and Google are not allowed to operate in China.
“We can take this for granted in a country like Ireland or in the US where there’s a strong rule of law and respect for human rights. But in a lot of the places around the world, those aren’t a given.
“What we see is that there are some competing visions for how the internet goes and what the future of that will be.
“We see a lot of pressure in a number of countries localising data in a way that could put people’s data more accessible to governments and in harm’s way,” he said.