ZeroMQ blocking one-to-many pattern

I have read through the zmq documentation and think I understand the 3 basic patterns: req/rep, pub/sub, push/pull. However, I don't see how they allow me to construct something where A sends messages to both B and C, with blocking behavior. That is, let's say I set a limit to 1024 messages for both A->B and A->C. Then, if a queue fills up, I would like A to stop sending messages, until there is room in both receivers, instead of just dropping the messages (pub/sub). push/pull does not deliver each message to both A and B, but only one of them.

Is there a way to do this with zmq?

Thanks!