Little Bastar**, i had my E46 Coupe keyed from end to the other by some little scroats high on white lightening cider, it really gets to me as its completely pointless vandalism. The do it because they know they can get away with it, and even if they are caught they will get a caution and let on their merry way. Unlike the motorist who might travel 3mph over the speed limit and get shaf**ed for £60 and 3 points. There is no justice.
Rant over, and i am sorry to hear your z was keyed, i know exactly how you feel.