Zoho Projects or Zoho Wiki for student collaboration

I'm thinking one of these products would be great for my chemistry class, since we work in assigned groups. It would allow us to talk with each other, share information, share notes, ask each other questions to better understand certain concepts, and schedule in-person study sessions if we need to. I'm trying to figure out which would be better Zoho Wiki or Zoho Projects?

Thanks for the input.

P.S. Do either products support voice or video chat? What about multiple users editing a document simultaneously?