For light oil, the normal ZC will be too much. It is a very versatile medium condition ball. The ZC Red Pin or a Punisher would be a better choice for medium-dry and broken-down lanes.
The IZ is a strong ball, even with the polished surface it comes with. More traction and control than a ZC, and I think better suited for medium to medium-oily conditions. Smoother, and if you sand it it should handle a fair amount of oil.
For medium conditions, though, I'd rather recommmend the ZC, an Absolute Inferno or, if you want an edgy reaction like a Punisher on more oil, a Smokin' Inferno.
The WZ is an older ball (not in the current big B line-up), with a medium load particle coverstock based on PK18, matte finish. Cannot tell much about it. As an alternative from the current range, I'd suggest a Strike Zone as a reactive alternative for heavy oil or an Ultimate Inferno.
Just my personal recommendations, hope it helps.
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DizzyFugu --- Reporting from Germany
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