cannot attack target on sky cuz NPC will attack us and we cannot atack him and it will kill us easily cuz quest item is lower damage. alsoif i start combat and fly dow for unmount and fight it will be finish combat

Thank you for the report.
It's a known issue, described at point 3 in the linked thread.

The quest is doable (did it myself), you just have to find a point around The Ocular where he will aggro you, then you can deal damage with the Eyesore Blaster.

Will mark this as a low priority for now.