Originally Posted by jekyl_hyde
Being that those are the only characters that have said anything (or made an inference) to Ichigo about Isshin, it makes me think Isshin was Zero squad.
Never said he wasn't. Said it was unlikely given how powerful the members of Zero Squad are.
I'm beginning to theorize that Yoruichi has always been a liaison to the Spirit King, and Kisuke was her top operative (or even he was possibly Zero squad).
Except we know this to be false. Yoruichi was the former captain of the 2nd Division
(before Soi Fon) as of 110 years ago. Urahara was the former 3rd seat of the 2nd Division
before he was promoted to captain of the 12th
. They held these spots until they went into exile following Aizen creating the Vizards.
Being in Zero Squad is a promotion from Captain.
They abandoned their captain seats.