I think there are some truncated expressions here.
(a) ἃ καὶ λαλοῦμεν
(b) οὐκ ἐν διδακτοῖς ἀνθρωπίνης σοφίας λόγοις [λαλοῦμεν],
(c) ἀλλ’ ἐν διδακτοῖς πνεύματος [σοφίας λόγοις λαλοῦμεν],
(d) πνευματικοῖς πνευματικὰ συνκρίνοντες.
My initial reading is that the dative πνευματικοῖς is an obvious change of phrase, not continuing the previous phrase, but being part of the phrase boundary of συνκρίνοντες.
I suppose it is possible to read the passage as
(a) ἃ καὶ λαλοῦμεν
(b) οὐκ ἐν διδακτοῖς ἀνθρωπίνης σοφίας λόγοις [λαλοῦμεν],
(c) ἀλλ’ ἐν διδακτοῖς πνεύματος [σοφίας] πνευματικοῖς [λαλοῦμεν],
(d) πνευματικὰ συνκρίνοντες.
This reading would take the phrase πνευματικὰ συνκρίνοντες to be a summarizing τὰ διδακτὰ πνευματικά. 'Taught words of man's wisdom' vs. 'Taught spiritual words of spirit wisdom.'
Here is BDAG's entry which interestingly gives both meaings 1 and 3 to this verse:
① to bring things together so as to form a unit, combine (Epicharmus et al.; Pla.; Aristot., Metaph. 1, 4, 985a, 24) so perh. πνευματικοῖς (neut.) πνευματικὰ συγκρίνοντες giving spiritual truth a spiritual form (Goodsp., Lghtf., BWeiss, Bousset) 1 Cor 2:13 (s. 2b and 3 below).
③ to clarify on the basis of a compatible relationship, explain, interpret (Polyb. 14, 3, 7; Gen 40:8, 16, 22; 41:12f, 15; Da 5:12 Theod.; JosAs 4:14 [ἐνύπνιον]) πνευματικοῖς (masc.) πνευματικὰ συγκρίνοντες interpreting spiritual truths to those who possess the Spirit 1 Cor 2:13 (s. 1 and 2b above) so NRSV text, PSchmiedel, Heinrici, JSickenberger.—FBlass and JWeiss propose emendation of the text.—M-M. s.v. συνκρίνω. TW.
Arndt, W., Danker, F. W., & Bauer, W. (2000). A Greek-English lexicon of the New Testament and other early Christian literature (3rd ed.) (953). Chicago: University of Chicago Press.
Unless the phrase πνεύματος πνευματικοῖς is a set phrase used in Patristic literature and elsewhere, I would be reluctant to separate the instrumental dative πνευματικοῖς from συνκρίνοντες; the two words seem made for each other; 'comparing the spiritual with the spiritual' (and not with the human elements of life).