vṛṇīmahe tvopādhyāyaṁ
brahmiṣṭhaṁ brāhmaṇaṁ gurum
yathāñjasā vijeṣyāmaḥ
sapatnāṁs tava tejasā
vṛṇīmahe - we choose; tvā - you; upādhyāyam - as teacher and spiritual master; brahmiṣṭham - being perfectly aware of the Supreme Brahman; brāhmaṇam - a qualified brāhmaṇa; gurum - the perfect spiritual master; yathā - so that; añjasā - very easily; vijeṣyāmaḥ - we shall defeat; sapatnān - our rivals; tava - your; tejasā - by the power of austerity.
One must approach a particular type of guru to execute a particular type of duty. Therefore although Viśvarūpa was inferior to the demigods, the demigods accepted him as their guru to conquer the demons.