R.Now here is my question.
I have been to New Zealand, but now I am in Taiwan.
When an interviewor asks me, "Where else have you studied?"
Can I reply, "I have studied in New Zealand for half a year" since I am not in NZ right now?
Yes, you can. "For half a year", or better "for six months", is not a defined time in the past, so it doesn't need the simple past tense.
If you were still in NZ, you could say "I've been studying in NZ for six months."
For other examples I read in the books, it seems that when I use "Present Perfect + for +time" the status should remain the same. For example:
Jill has been in Ireland for three days. (So Jill is in Ireland now.) <=Essential Grammar In Use page 44
They have been married for five years. (So they are still husband and wife now) <=Essential Grammar In Use page 44
The above two sentences use the past participle of 'be', as does my example above. So, it is a little different from "I have studied ..."
Iíve lived in London for a long time. (So I still live in London now.) <=Essential Grammar In Use page 46
But in my case, if I answer, "I have studied in New Zealand for half a year." Doesn't that mean "Now I am still studying in New Zealand", but it is not the real situation. I am in Taiwan now.
No, it doesn't mean that. Without a context, the sentence could mean that, but you have supplied a context in which the meaning is different.
The meaning, in your context, is "I have studied in NZ for a period of six months at a time which I'm not specifying."
I wonder if it is better to say, "I have studied in New Zealand and I studied there for half a year" to avoid a grammar miss.
You could, but a better solution would be to use the simple past:
"I once studied in NZ for six months."
"I studied in NZ for six months in 2006"