Killix_Kreed
If you put species into categories being the lower rank and the higher rank the MC's species evolving to a [Zombie Lord] means he has become a higher life form or entity from a Zombie(Lowest-rank) -> Zombie Lord(Higher-rank). So to put a dragon is also on the Higher rank of the species, a dragon can topple down a country to most fantasy stories a zombie lord a higher life form is comparable to a dragon.
I can understand how the protagonist's evolution works, he for being an S rank monster gains more status and abilities than low rank monsters making even he being low level doesn't change the fact that he is a scary S rank monster , this is because the system has given him the ability to improve his bloodline and increase his rank, which I assume is not possible for others and is only accessible to him