We don't know the personal background of ZO, and the frat is known to make exceptions.
JW-ZO-AB-HT-BB-others vs. JR-CR-MB-DR-LS-others?
A strong split with friction between the two groups might imply that members of JW's group are less likely to be culpable in LS's disappearance; since given the Smallwood altercation, they could not count on support or protection from JR or MB. Therefore, if JR or MB misrepresented the facts, they were only protecting themselves and/or CR.
ZO, AB, and BB are all from Indianapolis. They went to high school together. BB apparently worked for ZO's dad's company this summer.
My daughter went to IU and told me that it is highly unlikely that the ZO/AB group would hang out with the CR/MB/LS/DR group.
The only connection I can come up with is that ZO might be a candy salesman.
As far as JW goes, it looks as if he might have been on the edge of the JR/CR/etc. group. If he was spending most of his time with LS earlier in the school year, that would explain how he was on the edge of a group.
The original report about a "friend of the boyfriend" punching CR was from a "witness." I think that "witness" was a friend of ZO's (AB? HT?) and the statement was made to mask the true reason for the fight. (anger at CR for letting LS talking loudly at the bar about what she had been taking that evening).