Doomsday: I Can Synthesize Zombies Limitless

Leon traveled to the doomsday, where the zombies were rampant and humans were constantly fighting inside.
When Leon was desperate, he suddenly activated the divine-level zombie synthetic system.
As long as the zombies lost their resistance, they could be merged, and after synthesis, they would unconditionally follow his orders!
Ding! Congratulations to you for combining two level-1 zombies into one level-2 ordinary zombie. Reward the refined steel knife *1 and all element points +10.
Ding! Congratulations to you for combining two level-10 zombies into one level-1 zombie, and a reward of 1000 potential points!
In addition, Leon found that the synthetic zombies would also give out extra rewards every day, including cultivation methods, medicines, skill points, and potential points.
Facing the siege of zombies, others could only run for their lives crazily,
Only Leon rushed up with ecstasy
One day, Leon found that he couldn't find the zombies that could be combined.
"What? I turned all the zombies into subordinates?"