How come they write it Nazi instead of Nati?
“Z” is pronounced like “s” in German.
Do Germans say “Nah-see?”
In German, the letter Z is pronounced "tset". The "t" is not silent, but inflected.
"Nazi" is thereby pronounced "nah-tsee" -- which sounds very close to "naht-see".
Do Germans say “Nah-see?”
That must be why they in common speech started first calling themselves “Nazis” mention National but shorter, and then writing Nazi instead of Nati which would have been pronounced Nah ti.