I know what ZeroMQ does. But you argue that a one can easily write a broker on top of ZeroMQ that provides persistency, but that invalidates your biggest reason

I know what ZeroMQ does. But you argue that a one can easily write a broker on top of ZeroMQ that provides persistency, but that invalidates your biggest reason of using ZeroMQ, namely brokerlessness. Besides SPOF is not an argument. All serious brokers have supported clustering and failover for quite a while, and they support persistency. I don't see a good reason why you may want to write a ZeroMQ-based broker instead of just using RabbitMQ.