Zoro was right and Ace's example is pretty spot on if you think beyond the obvious, which seems like some have a hard time. You can't keep someone in a birdcage to keep them from being in danger or you can't fight all of their battles. Everyone has their own life, you have to help when you really need it.
In the current situation, it's ridiculous to go to Alabasta, it would just be a waste of time and maybe when Vivi needs their help, they won't have time to come back. And it's ridiculous to go to Mary Geoise and risk losing some nakama or losing your life and even if you win you don't get any information from Vivi. The prize is not worth the risk.
When they have information about Vivi, even if she is going to be executed like Ace, then they will go save her no matter what and risking their lives, like Luffy did with Ace.
It doesn't matter if they manage to save Vivi or in the end she dies like Ace, the important thing is that they move heaven and earth and do everything in their power. Nothing more can be asked of him.
As concerned as they may be, One Piece is a pretty rudimentary world with little technological quirks. You can't find a person without a Vivre Card. It only remains to wait for her to get in touch or for the newspapers to publish more information.
For this Zoro is right and the comparison with Ace makes sense.