Who hath known? (tis egnō̇). Second aorist active indicative of ginōskō, a timeless aorist, did know, does know, will know. Quotation from Isa 40:13. Quoted already in 1Co 2:16.
Counsellor (sumboulos). Old word from sun and boulē. Only here in N.T.
His (autou). Objective genitive, counsellor to him (God). Some men seem to feel competent for the job.