Zoro stopped the attack for long enough that:
- He could warn the other SN to escape
- The other SN dodged
- We see the attack destroying part of the island
After that was when Zoro was overpowered, and he took some of the full impact of the attack before Law teleported him. Zoro didn't completely tank the attack, but he still endured it for a bit before he was rescued.
If an attack last 3 seconds and you withstand it for 1 second, it's still a feat. Anyway, Hakai >> Hakoku> Ikkoku Sovereignty ~ Thunder Bagua.
Everyone on the Rooftop can tank a Thunder Bagua.