zhì​yú HSK6

as for

至于 (至於) zhì​yú
as for preposition
regarding or as to; used to transition to a new or related topic

As for that question, we'll talk about it later.

go so far adverb
to reach a certain degree or level, often used in the negative to suggest an extreme is unlikely

Surely he wouldn't be unable to do even such a small thing well.

Frequency

Movie subtitles
21.9 per million appears in 10% of films
Written text
60.8 per million

Details

HSK 2.0
Level 5
HSK 3.0
Level 6

Sources

Definitions
CC-CEDICT