How do you kill big zombies with a sledgehammer in a yellow jumpsuit? (Dying Light)

I tried to kill one, but so far I have not succeeded - I tried to drive him through water with electric current and gasoline with fire (it seems that they have no effect on him), hit him in the head several times and ran back. But while he lives. How long does it take to kill him, or is there an easier way to do it?