User blog comment:12th Supernova/Chapter 815: Germ Warfare/@comment-24850639-20160204161726/@comment-10543621-20160206045011

That was Pekoms calling Luffy back. Not Zoro. Zoro is just being tsundere. He obviously cares enough about Sanji. That's why he was sitting outside listening.

And yes, Law had something he wanted to talk to Luffy about, and that was about how Zou isn't a suitable hiding place anymore and they should leave Zou soon because they'll bring further trouble to Zou if they stayed on. Of course, Luffy took the chance to tell Law about the Sanji situation as well, but he did get his point across in the end.