μηδὲν ἐλλείπειν: lit. ‘to fail in nothing’, so ‘to leave nothing undone’ (F.). For ἐλλείπειν see note on ad N. 33.
οὑστινασοῦν: strictly speaking this is a case of attraction for οἱτινεσοῦν εἰσι, since ὁστισοῦν, ‘whoever,’ introduces an indefinite relative clause; cp. the use of the Latin quicumque.
μηδὲν ταλαιπωρηθεῖσιν, ‘without any painful effort.’