Zoro, on the other hand, doesn’t need to issue a command. He doesn’t even register the fodder, lost in thought about Enma and facing away from them, towards King.
Zoro’s Conqueror’s Haki is so strong that he can simply passively KO fodder. This is different to even Shanks, who was actively using his Conqueror’s Haki to display dominance in front of Whitebeard and his crew. Let’s not also forget that Zoro is a newbie. He shouldn’t have that level of control over Conqueror’s Haki, when only a short while ago, he didn’t even realise he had it. Luffy had the basic form of Conqueror’s Haki since Amazon Lily, but wasn’t able to use it on command until after the timeskip.
Then again, it shouldn’t be surprising that Zoro’s Conqueror’s Haki is stronger. This man suffered a crippling injury at the very beginning of the story, but proceeded to take on a Logia, an elite martial artist and assassin, absorbed all of Luffy’s pain and tore through an entire island of humandrills before Mihawk even started training him. Zoro’s fighting spirit is the strongest in the series bar none.
If Haki = willpower, it’s no wonder that Zoro’s is above all others. No one can compare to his determination.
*by Den_Den_Mushi