Whereas (οπου). Loose use of οπου (in Xenophon) = "wherein."

Though greater (μειζονες οντες). Than the evil δοξα. Concessive participle and comparative adjective.

In might and strength (ισχυ κα δυναμε). Locative case. Both indwelling strength (ισχυς, Mark 12:30) and ability (δυναμις, Matthew 25:15).

Railing judgment (βλασφεμον κρισιν). "Blasphemous accusation."

Against them (κατ' αυτων). The evil angels (δοξα).

Before the Lord (παρα κυριω). In God's presence. See Jude 1:9 and possibly Enoch 9.