It sounds like normal sibling behaviour, you will just have to keep an eye open. Make sure they're not alone when high value items are about.

As for other dogs, it sounds like Zeb is asserting himself, try putting him on a lead everytime he does this to show him that if he acts this way play will be ceased, don't put them both on, just him, he'll soon learn that this is undesirable behaviour.

Reward him when he plays nicely too, show him the alternate behaviour that you want from him, this way it will be easier for him to understand

I have no idea about behavioural issues with malamutes but I think there are a few experienced ppl on here that may be able to help you too.

Hope I have made sense

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