In this thread I will give my point of view of the Zetsu's. Ok here we go:
• Zetsu's are technically computers, they all originate from one source, that is Hashirama's Vessel.
• Zetsu's have a database where they all store knowledge, that is too Hashirama's Vessel, so if Zetsu #1 collected information, he stores it in the database(Hashirama's Living Tissue) and then Zetsu #2 or Obito could access this same information of Zetsu #1.
• I believe Zetsu has a type of Dojutsu, specifically a type that can record his sight and vision, and store it in his database for later viewing, as seen here:
• They are part of mother earth, this is because Hashirama's Mokuton is the source of all living things.
Because of this they cannot be sensed by even the Byakugan, because they can blend with nature. They can even join bodies with trees and any natural element.
So here is my little theory.
I think Sennin Mode users can connect to this database too, because they use mother natures energy, same as the Zetsu. So imagine Orochimaru paying a visit to Madara's Labs (Since he knows where it is thanks to Kabuto) he then places his hands on the Hashirama Living Vessel and transforms into Sennin Mode, he can then get access to the database and steal as much as information or even see through Obito's eyes.