I don't think, that there is any difference, when used in a question.
But looking at the answers there is a difference.
machen is usually followed by a substantive
Ich mache meine Hausaufgaben.
tun is followed by a verb. At some very colloquial level I would say
Ich tue gerade lesen
but some how feeling it isn't good style, I changed it while writing the answer to
Ich lese gerade ein Buch.
Which doesn't contain the verb
tun. I'm not sure whether all examples I can think up are in some way colloquial.
machen is used in context, when something is produced, while
tun is describes spending ones time.