It's a nested file within a nested file within a nested file within...

The file contains 16 zipped files, which again contains 16 zipped files, which again contains 16 zipped files, which again contains 16 zipped, which again contains 16 zipped files, which contain 1 file, with the size of 4.3GB.

What's the password

42

Wtf

I know, right?

Now, imagine that 4.9 x 16^5

But what's the purpose of it?

Just to show how good something can be archived?

When you unzip it, it opens a black hole

So how much is that in total

Look at the screenshot

Oh god

It's a Zip Bomb.
Basically it's a method to disable antivirus systems, instead of breaking the antivirus or avoiding it, it is purposefully opened by the antivirus. And thus, given the prohibitive amounts of space you need to do so, the antivirus freezes, giving an opportunity to a virus to do it's job.

It's not harmful per se.

But it can be dangerous.

So what happens if I unzip it

Although most modern antivirus can detect and skip zip bombs.

Do you have 4.5PB of space?

It's like an emp bomb