Alright lets break this down.
Pre time skip nusjuro weilding his blade which is not a permanent black blade. Black shading on top white shading on bottom of blade.
Unsheathing blade with the same black shading on top and white shadingon bottom, this is the same as pre time skip no haki applied.
Zoro with his non haki blades with the same black shading on top and white on bottom no haki applied.
Both user coat there blades in arnament haki... your cope is finished nusjuro does not have a permanent black blade nor will e ever be stronger than Mihawk.