Like his Replicants, he is either physically degenerating, or the only part of the fatal disease the original Zin managed to cure with the cloning process was the respiratory illness, explaining why he looks physically wasted like the original Zin, but doesn't need the oxygen bottle. The disease is still killing the clone, though, and is affecting his mind in particular, which explains his irrational behavior such as killing his henchmen for trivial reasons and his sudden mood swings.