@Bogdan. Welcome! Use [pawn] to light up the code. All one needs to do is change blast to radiation. It will chew on the armor first then when none is left hp. This plugin is set up to use radius damage. There are several damage types to choose from but nothing where anybody can easily randomize radius damage by armor 20-30 at wack unless you use timebased. That's close to what you want without spending a lot of time on it.
There's nothing in posted code to "turn the human to zm". Besides don't abbreviate stuff like that please. Zombie plugins are usually a series of plugins. The turn function is likely on another plugin or I'm blind but I didn't notice your little side bar until I finished with the damage comment. Start with changing blast to radiation for instance and go from there.