I’m typing this up because it took me far too long to find, probably because I wasn’t using the right search terms, or because I was trying stupid key combinations…
In any case, if you want to make international characters (that is, characters with accent marks, diacritics, trema (plural tremata), umlauts, eat that google!) such as ë, é, ê or even ö or ï and so forth on the HTC Desire Z hardware keyboard, you simply long press the base character. A menu pops up and you get to choose the accented character that you would prefer to insert at that moment.
I sincerely apologise for interrupting your usual high IQ programming with this. If however you stumble upon this post and it helps you, why don’t you leave a comment just for laughs?