Overall, I think there is an intentional movement from the periepath/sate in v. 2 to the peripath/swmen in v. 10, with the main clause highlighted in v. 4. Therefore, I think there is some emphasis as to what the main clause in v. 4 means for us now. That we were dead in sin is juxtaposed to that we are now alive in Christ. And that we once walked in the age of this world is juxtaposed to that we now are to walk in the good works prepared for us by God. Also compare the e˙n of verses 2 and 3 with that of v. 6, 7, 10. There are two types of contrast: past/present and apart from Christ/because of Christ. The hinge of both of these is v. 4, but God... made us alive in Christ! That the main clause is found in verse 4, Christ made us alive together with Christ! This is supported by the concessive statement of v. 3 that we were dead in our sins. Paul really tried to makes this clear by repeating what he has already said in vv. 1-3. The intention is that the reader might be blown away by juxtaposing such contrary realities. Dead in sin to alive in Christ . That is amazing. Just straight out-of-this-world amazing. The action/manner of this work is emphasized: by grace through faith, that is, not of your own doing, it is the gift of God. Again, not of your works, so that no one should ever boast. You should never boast because we are his workmanship... (v. 10).
καὶ ὑμᾶς ὄντας νεκροὺς τοῖς παραπτώμασιν καὶ ταῖς ἁμαρτίαις ὑμῶν
And although you being dead in the trespasses and sins
ἐν αἷς ποτε περιεπατήσατε
in which you formerly walked,
κατὰ τὸν αἰῶνα τοῦ κόσμου τούτου κατὰ τὸν ἄρχοντα τῆς ἐξουσίας τοῦ ἀέρος τοῦ πνεύματος τοῦ νῦν ἐνεργοῦντος ἐν τοῖς υἱοῖς τῆς ἀπειθείας
according to the course of this world, according to the ruler over the domain of the air, (and) over the spirit that is now at work in the sons of unbelief--
ἐν οἷς καὶ ἡμεῖς πάντες ἀνεστράφημέν ποτε ἐν ταῖς ἐπιθυμίαις τῆς σαρκὸς ἡμῶν ποιοῦντες τὰ θελήματα τῆς σαρκὸς καὶ τῶν διανοιῶν καὶ ἤμεθα τέκνα φύσει ὀργῆς ὡς καὶ οἱ λοιποί
in whom also we formerly lived in the passions of our flesh, doing the desires of the flesh and the mind, and we were by nature children of wrath, like the rest.
ὁ δὲ θεὸς πλούσιος ὢν ἐν ἐλέει διὰ τὴν πολλὴν ἀγάπην αὐτοῦ ἣν ἠγάπησεν ἡμᾶς
But God, being rich in mercy, because of the great love with which he loved us,
καὶ ὄντας ἡμᾶς νεκροὺς τοῖς παραπτώμασιν
(although) we were dead in our trespasses,
συνεζωοποίησεν τῷ Χριστῷ
(he nevertheless) made us alive together with Christ --
χάριτί ἐστε σεσῳσμένοι
by grace you have been saved --
and raised us up with him
καὶ συνεκάθισεν ἐν τοῖς ἐπουρανίοις ἐν Χριστῷ Ἰησοῦ
and seated us with him in the heavenly places in Christ Jesus,
ἵνα ἐνδείξηται ἐν τοῖς αἰῶσιν τοῖς ἐπερχομένοις τὸ ὑπερβάλλον πλοῦτος τῆς χάριτος αὐτοῦ ἐν χρηστότητι ἐφ' ἡμᾶς ἐν Χριστῷ Ἰησοῦ
(he did all this) so that in the coming ages he might show the exceeding riches of his grace in kindness toward us in Christ Jesus.
τῇ γὰρ χάριτί ἐστε σεσῳσμένοι διὰ πίστεως
For by grace you have been saved through faith.
καὶ τοῦτο οὐκ ἐξ ὑμῶν
And this is not by your own doing;
θεοῦ τὸ δῶρον
it is the gift of God,
οὐκ ἐξ ἔργων
not out of works,
ἵνα μή τις καυχήσηται
so that by absolutely no means possible never ever should one boast.
αὐτοῦ γάρ ἐσμεν ποίημα
(you should never ever boast because) we are his workmanship,
κτισθέντες ἐν Χριστῷ Ἰησοῦ ἐπὶ ἔργοις ἀγαθοῖς
being created in Christ Jesus for good works,
οἷς προητοίμασεν ὁ θεὸς
which God prepared beforehand,
ἵνα ἐν αὐτοῖς περιπατήσωμεν
so that we should walk in them (now).