does a specific Zetsu need to touch someone to be able to transform into them?
from this chapter, it seemed like one Zetsu wasn't aware of what the other was doing, but if it's every zetsu to himself, it's still problematic for them because each of them needs to fight and survive a battle in order to get himself a "spy suit". and if the information we've been told about the number of deaths is correct, then it's still a big problem for the zetsu team.