Maybe he used armament, maybe zoro leaked some stored haki, or maybe king was more focused, who knows how that works
Why couldn't Zoro cut Kakus leg while he didn't even use tekkai in egghead, does he have dura neg? Things happen
Fact is from what we have seen the children seraphim are more durable than king who got damaged multiple times during the raid by multiple people meanwhile the seraphim did never, that way my original statement
meanwhile you came up with some random nonsense where "macro was supposed to fight king and that's why he was bleeding" in the same chapter marco verbally declares he is not fighting king or queen