Translation:Vanya, why did you take apart the camera?
зачем asks about purpose, intention, future, while почему asks about cause, past reason. The answer to the question above would be e.g. to repair it, to see how it works. If you asked почему, you'll get an answer like because it stopped working, because mom asked me to do it etc.
Of course the difference in meaning could be quite big or barely noticeable, depending on the specific question/context.
I was wondering the same thing. I found this. http://www.yearlyglot.com/when-and-how-to-use-zachem-and-pochemu/ I understand that zachem is a little more emotionally involved as in for what purpose did you break this cup. I stand to be corrected by anyone as i am a novice myself, just some shared info.
I think he means the prefix разо in разобрал. Using the phrase "take apart" in English also implies that this is a compound verb in Russian! So I had a look at Wiktionary and it appears разобрать is indeed formed the same way! :-o разо "apart/ asunder" + брать "to take". Good to know! :-)