I had the same question and emailed Bundesagentur für Arbeit (BA). In my case, the officer said that, with the internship

- study-related, and
- less than 90 days within 12 months, and
- during my study after 4th semester in H+ institution

and thus

- under 15.6

there is no need for ZAV pre-approval ('Einvernehmen'). Because it is not considered an employment (BeschV § 30 Nr. 2; Nichtbeschäftigungsfiktion (16a.15.8) from [here](https://www.arbeitsagentur.de/datei/dok_ba146473.pdf)). Therefore you only need legitimate way of entry + stay for 90 days (e.g. with your EU residence permit/visa-free passport/...).