Hmm.. cazzimm.. I dunno if there is an exact word for it in English.. ma teng a cazzimm Zidanie!
It is a mixture of meaness, egoism and spite.. but somehow not exactly a negative. I suppose the word "furbo/a" (wily, sly, underhand, streetwise, clever) is the one I would prefer over cazzimm.
The reason Neapolitans don't fall for scams like this is because they invented them first.. this makes them "cazzimm".. one step ahead.