No idea of any past problems. Although Zidane played a few years w/Juventus of Italy while Matterazzi was in Serie A. He's a pretty easygoing player. I've never seen him mix it up much.
Zidane had no comment. Most of the French players said they didn't know. The French coach blamed Matterazzi for "getting" Zidane tossed. I guess he thought Matterazzi was faking. Didn't look fake to me, or to any announcer watching, or anyone I've talked to.
Matterazzi had no comment, either.
I guess it'll remain a mystery.