How to open the treasure chest in zombie hunting mode?

How to open the treasure chest of zombie hunting ground mode;

1, no strategy, only character.

2, nine boxes of open pike.

3, two boxes of long knives, good luck.

4. A box with a black knife? Is it hot enough? Just after the update on June 5.

Now I also suggest storing more before opening the box. Generally, there are at least 10 cases. Personally, I think.