Easy or hard?

Is it easy or hard to make an exe Archive with C++
If it´s not to hard, could someone show me a small example

It's extremely difficult.

First off, you need to have your decompression code, such that it doesn't take up a stupid amount of space (i.e. 20K max, and even then that's a bit too much overhead).

Second, you need to work out how your program is going to know that it has compressed data appended to it, otherwise it needs to exit gracefully rather than amusingly trying to decompress itself.

I did make one, but it was under contract so I'm afraid I can't show you any code...but take it from me, it's not easy.