Can't say for sure, but my hunch is that it is the second option. The way I am imagining it being said, I think it has sort of a "is that so? / you don't say?" connotation to it.

Anand's answer isn't wrong, but the phrase can be both a revelation (like Anand's answer), or a statement, depending on the context.

Japanese often use a person's name in place of a pronoun when speaking informally, even in the first person. If perhaps you confessed that you like the speaker, this would be an appropriate response...something akin to: "Yeah, I like you too."

Hope this helps.

Troy

I agree with the answer of anand!
They were talking about something and the speaker was surprised (he did not expected to hear that) to know that Zoi also liked it, too.

I would not say "Zoi mo suki nanda" as "I like you too, Zoi". I would say, "Zoi (no koto) ga suki nanda".

Now, if the speaker is talking about several people that he likes, then mentions about Zoi lastly, yes, you can say that. For example, "I like Junko, Miwa, and Zoi, too". This sentence should be translated as "Junko ya Miwa, sorekara Zoi mo suki nanda..."