Something's Not Right with My Crafting System

In the apocalypse after a world war, everything is in chaos, with mutated beasts running out of the laboratory, and out-of-control genetic warriors... But for Zhang Yuan, who has a synthesis system, these are not a problem What is this? Synthesize it Mutated rat (corpse) + mutated rat (corpse) =? ? ? Confirmed synthesis: Mutant Zombie Rat! ! Gene warrior (corpse) + gene warrior (corpse) =? ? ? Confirmed synthesis: zombies! ! ! Don't zombies only exist in movies? ? I actually created it? ! Something's not quite right with my crafting system...