As you can see at the Bottom left of page 15 of chapter 598 Narutos Face is disfigured and resembles Tobis Mask, so he could be Copying Narutos Face and when it is revealed next week Tobi will look like Naruto confirming he is a Zetsu Clone?
i'm not sure it's hard to tell. Depending on the way you look at it it could very well be true. However if you look just below naruto's forehead protector, you can see his nose, and that his face is pointing directly down. That odd face looking blob could easily be his shirt - the 'eye's' of that blob look like his necklace thing, and the mouth thing looks like the seal on his stomach... so yeah, could just be a bad drawing
As you can see at the Bottom left of page 15 of chapter 598 Narutos Face is disfigured and resembles Tobis Mask, so he could be Copying Narutos Face and when it is revealed next week Tobi will look like Naruto confirming he is a Zetsu Clone?