Board Thread:Manga/@comment-38849221-20190321163015/@comment-33077628-20200613164040

I understand that Zeke wanted to save his little brother, but there was a lot at stake here. He didn't have much time left and his plans or Eren could have been discovered at any moment. He was hard pressed to achieve his goal as soon as possible. As far as Zeke knows, Eren came all the way to Liberio, which was a good sign of trust already. He could have told his plan to sterilize all eldians to the warrior squad and prepared them to take Eren's Founding titan if he betrayed him when they would have shaken hands at Liberio.

Had Zeke then confirmed that he was the one "in charge" of Ymir, he could have sterilized all eldians right there, done. After that, all of the shifters could have titanized, grabbed their families and flead to Paradis. Though, I think Zeke would have to kill Historia to end the royal bloodline and make sure his plan would not be undone.

Had Eren betrayed Zeke, trying to use the Rumbling then, even if he did succeed, Zeke could have attacked Eren with the help of the other warriors, have one of them eat Eren and stop the Rumbling right after, which would be in the best interest of the warriors who would want to save their families.

In the end, Zeke would have to make a gamble and touch the Founding titan at some point. I still have difficulty to understand why did he wait to do it in Paradis, surrounded by his enemies, when the fate of the world was at stake.