Zoro is not using haki. He stopped using haki here.
It would help out if you read the manga.
Zoro cut Kaido with all three swords. If he didn't then he would have stayed he didn't. You can't determine the number of swords Zoro use by the number of cuts he leaving his opponent. That's not how the manga works.
Look at Kaku. 9 sword style yet 1 slash/cut.