I think Zippy is that consumed with hatred & jealousy towards Helen, that she will not allow him to have any form of coparenting relationship with her & she’s forced him to pick her over his kids. And he’s a weak, pathetic, selfish man & happy to do so. The kids are better off without a parent who doesn’t want to be involved & when they are teenagers with their own minds, they will realise what an hole he is. Thankfully, Helens Dad & Brother seen to be very positive male figures in their life & show them how a proper father behaves.