The pairing with Parashah Pinchas, whose opening verses reward Pinchas's zealous action against public idolatry with a covenant of peace and a hereditary priesthood, rests on Elijah's own explicit description of himself in this haftarah as very zealous for God, language that directly echoes the zeal for which Pinchas is rewarded at the very start of his parashah, two figures generations apart both defined by the same quality of uncompromising devotion.
Where Pinchas is rewarded immediately and publicly for his zeal, Elijah's own zeal leaves him instead exhausted, afraid and asking to die, a harder and more complicated portrait of what such single minded devotion can cost a person even when it is entirely justified, extending the parashah's celebration of zeal into a haftarah that also shows its very real personal toll.
Both accounts also close on the same structural note, a designated successor. The parashah closes with Joshua formally appointed to succeed Moses, and the haftarah closes with Elisha designated to succeed Elijah, so that both readings end not merely with a reward for faithful service but with an assurance that the work will properly continue once the current leader's own time has passed.