It seems "auf Wiedersehen" is the German version of the French "au revoir" and the Italian "arrivederci". They all follow the same format:
(auf/au/a) - onto/to/until
(Wieder/re-/ri-) - again
(sehen/voir/vederci) - to see / we see each other
so, basically, "until we see each other again" / "see you"
i put until next time and it accepted that. I mean, technically in English we would more likely say until next time, as opposed to saying until we see each other again, and accept them as interchangeable it just adds further to the confusion about what exact terminology you're using. :/
Tschüss means bye. And auf weidersehen means till we meet again. Its like the difference between guten tag and hallo. One translates to good day, and the other translates to hello. It informal and formal. Another example which may help somewhere else is du and Sie, Sie is like, sir and du is just you. Now Sie is very different from sie, though spelled exactly the same they mean very different things. One is a noun while the other is a pronoun so its easy to tell them apart, because all nouns are capitolized and pronouns and nouns are used differently in sentences. Though I am assuming, it is possible that german sentences are formed differently than english. However as they are sister languages it is a safe assumption. I really hope this helped.
I looked up the IPA transcription and it's: /aʊ̯f ˈviːdɐˌzeːn̩/ the two dots after the 'e' symbolize a prolonged vowel, so yes, it is like 'ze-en' except you don't have to stretch it for long. The audio here: http://en.wiktionary.org/wiki/auf_Wiedersehen is nice and clear! If you listen carefully and for several times, I'm sure you'll understand! ~Hope I helped~
Being native Italian, fluent in French and not so bad in English I find the study of German so fun, to me lot of resemblance with english, but I'm sure native english won't agree. In other cases some words are similar to latin languages. Take "Zitrone", french "citron" italian "limone". And many many more.