If Tobi was somehow a clone of zetsu, like many people suggest, shouldn't Naruto know that already since that he can detect zetsus with his Chakra mode ?
naruto detects the malice of people, that's why he could detect the zetsu's from the shinobi. tobi is also a bad person, the worst, so I don't think there can be any differentiation between them even if he is a sort of zetsu formation.
honestly I'm not conviced he is a zetsu clone but more like a creation from madara and hashirama's cells, and the connection with zetsu is that zetsu was the first experiment befor creating tobi. my full theory description about it is here if you like to know the details of my thoughts:
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