The word can be broken into three simple componets, pimp as in hip and or cool,shiz originating from the word shit,as in the shit,natch originating from the word snatch as in worthy enough to steal. Can also be used in terms of sarcasm.
yo your ride is pimpshiznatch.
person1 "yo dog check out my kiks!"
person2 (sarcastically) "yea real pimpshiznatch."