Δελφῖνα νήχεσθαι διδάσκεις: ἐπὶ τῶν ἐν ἐκείνοις τινὰ παιδοτριβούντων, ἐν οἷς ἤσκηται → Teaching dolphins to swim: is applied to those who are teaching something among people who are already well versed in it
separately: P. and V. χωρίς, δίχα.
privately: P. and V. ἰδίᾳ (Eur., Supplices 129).
independently of: see apart from.