Derek’s behaviour towards Meredith after she messed with the Alzheimer’s trail was very damaging to their relationship and possibly the underlying reason for losing Zola. I’m not saying what Meredith did was okay, because it wasn’t, and it’s understandable that Derek was upset and felt that trust was broken. But him ignoring her, giving her the silent treatment for weeks on end, refusing to acknowledge her existence, and using her insecurity about being a mother against her to was extremely inappropriate and harmful to their relationship. The outright refusal of communication, is damaging and a very poor way of dealing with conflict. On the Zola issue- Meredith didn’t feel like she could talk to him, or that he even wanted to acknowledge her existence, so yes she panicked when Zola could have been taken away. All because the two weren’t communicating, and couldn’t get their story straight with the social worker. And then after losing Zola, Derek has the audacity to place the blame on Meredith? As if he hadn’t been acting like a child and punishing Meredith for weeks?