Responses
The dragons exist because of the red dragon king . If you remember at the beginning when they first saw Yona they got some kind of awakening . It's like that awakening was forcing them to serve the red dragon king . So if ever zeno ask them to leave yona they wouldn't do it . What Zeno did is the best way to collect all the dragons soul. I mean it is harsh since he was a dragon himself supposed to serve yona but those many years that he endured everything on his own , i think all his emotions are gone already . Even the love and passion he's supposed to feel towards the king it's all gone
I mean i get it after 2000 years i to would be tired but he shouldn’t make the decision for the others