This is mainly a Laurent question, since it's his property after all.
If I take code from SFML (but not copy verbatim a file, just a single method from somewhere) is it enough to put notice like that just above the method in .cpp file
//code below was taken from SFML Text.cpp and MODIFIED,
//it is NOT the original software, if looking for original software see:
//https://github.com/SFML/SFML/
followed by exact copy of zlib text that appeared in the file I took a method from?
So it goes like:
1. my code in my .cpp
2. that notice
3. SFML original (c) text
4. SFML code (modified or not)
5. end of file
I'd say I'm fulfilling all three: I don't misrepresent the origin, I plainly mark the (changed) copy as not the original and I don't remove or modify the original notice. (I feel a bit fishy about the last.)
Zlib lib/license FAQ doesn't really help, it talks more about what steps to take when releasing own fork of entire library.
http://www.zlib.net/zlib_faq.html#faq24