I tried to make a quest where you have to,

1. Kill 6 zombies in a certain area
2. Break 4 netherack
3. Return to the NPC who gave you the quest

Stuck on step 2, as the console says I am missing block durability, so I put it in as "1" (and tried with "0" too)

If I do the quest, I can get up to step 2, where I will get stuck and it won't tell me what I have to do next.

If I try to edit the specific step in the quest, I crash

Please help!