Zenithium in "Dragon Quest 3: HD-2D Remastered Edition" is a very special item in the game. If you want to get Zenithium, you can go to the navel of the earth. You may remember that in the last room Here, you can choose to go north or south, with the south initially being a dead end.
How to get Zenithium in Dragon Quest 3 Remastered
In Earth's Navel, you may remember that in the last room, you had the option of going north or south, with the south initially being a dead end. You could have interacted with the blue stone Zenithium on the wall, although you couldn't do anything before. Now, the magic ball changes all that.
Interact with Zenithium again and place the magic ball in front of it. After the bomb explodes, the blue stone will fly out of the wall completely intact. You finally got Zenithium. But why did you collect this thing in the first place? Return to your subordinates to get the next step of instructions.
At this stage, returning to your minions is not actually necessary, although you can still go to them for some tips.