Why we use here in this context "zu Deutsch"?

Question

In a German text, describing Russian sentences for Germans, they wrote a Russian sentence and after it > (zu Deutsch: …) That means its translation, but why did they write “zu Deutsch” instead of “ins Deutsche” or “auf Deutsch”?

Answer 1

This looks like a mistake/ incorrect translation. When I provide a translation in German, I always say "auf deutsch". The meaning of "zu deutsch" is actually "too German", which doesn't make any sense here.

Answer 2

Zu is "to" in English. The meaning of sentences using "zu Deutsch" is not so much that "this is in German", as it is "this has been converted TO be read/understood by a German"

Zu Deutsch ==> to German

There is a fine line between "zu Deutsch" and "auf Deutsch", which is that the former would be used mostly for whole sentences or figures of speech and the later for directly translatable words or sentence fragments.

Auf Deutsch ==> in German

HTH