Her turn: She attacks with Lord of extinction. I block with Voice with equipment. I assume nothing happens because the sword gives voice protection from black.
Question - If she lays Relentless Assault and she can attack again...can I block with voice with sword again causing it to cancel out again?
Yes, part of protection from a quality is that any damage from that quality is prevented. Since the Lord of Extinction doesn't have Trample, all of its combat damage is assigned to your Voice, but then prevented. Additionally, since your Voice is still alive and well in the second Combat phase, you will be able to assign the Voice as a blocker again.
Lord of extinction that is 28/28 and a few other creatures
My side:
Voice of Resurgence with Sword of Light and Shadow attached
Her turn: She attacks with Lord of extinction. I block with Voice with equipment. I assume nothing happens because the sword gives voice protection from black.
Question - If she lays Relentless Assault and she can attack again...can I block with voice with sword again causing it to cancel out again?