Just use the regular letter instead of the Umlaut

But that’s just wrong. ü has a different meaning and pronunciation than u.

If umlauts aren’t available, the correct way to write umlauts is with an additional e: zurueck.

Über-Mensch -> Uber-Mensch

Please be aware that this term can be problematic, since it can be seen as a foundation for fascist ideas. https://en.wikipedia.org/wiki/Übermensch#Use_by_the_Nazis

*zurück

Do C compilers support non-ascii characters?