Strange haki belongs to Zoro if you read closely you will notice Kaido himself doesn't seem sure where it's coming from
When Zoro hits him with tatsumaki he finally notices Zoro is carrying one of Oden's blades he never says that sword is the source.
Enma takes excessive amounts of it's users haki and uses that to slice more than needed Tenguyama is master sword smith that forged the Ame no habakiri which is on the same grade as Enma, i see no reason why he would hide if Enma had more abilities than he already explained.
Kaido would most likely pointed out if Enma was mainly responsible for scarring him especially being only second time that has ever happened, instead Kaido choose to credit Zoro for this feat we don't hear single word about Enma after he noticed it being Odens sword. This will just remain your head canon trying to twist shit for the sole purpose of undermining. He used all 3 of his swords to scar Kaido so we can actually say Sandai Zoro weakest sword has accomplished same feat as Enma
Enma is the same grade as Zoro Wado and Shusui i wouldn't call it more powerful than any of the swords on the same rank, it's far more difficult to use and master that is the only difference.