Above that, they don't have ACoC and forever stuck below HKs
Nope, not true regarding Zoro > Admirals even IF his AdCoC would be above theirs (I still have high hopes for Fujitora in this department).
Reasoning being Zoro has advantages but so do the admirals.
Zoro can't:
Fly
Move at speed of light
Easily dodge AoE attacks (Fujitoras meteors)
Easily dodge multiple attacks (Kizarus laser shower)
Grow out new bones (Ryukogyus bone crushing abilities)
Heal up a pierced or sliced body (All admirals)
So just because the Admirals might, or might not, lack the one tool to beat the HKs it doesn't mean that Zoro automatically beats the Admirals easily. The Admirals are all far better fighters than the HK. There are of course exceptions as I think Green Bull is quite crap and Shamrock is likely OP but generally speaking it doesn't work that way. In order for Zoro to beat Admirals he would need to somehow force them to fight his fight. On the ground, close to mid distance. King really should only have stayed far away and destroyed Zoros foothold to win, spamming fire attacks from a distance.