I’m curious, too. I looked just a little more closely. My understanding is really shallow, but, the following code in rrbroker.exs seems to handle multi-part messages:

def loop(frontend, backend) do
receive do
{:zmq, ^frontend, msg, flags} →
case(:proplists.get_bool(:rcvmore, flags)) do
true →
:erlzmq.send(backend, msg, [:sndmore])
false →
:erlzmq.send(backend, msg)
end
{:zmq, ^backend, msg, flags} →
case(:proplists.get_bool(:rcvmore, flags)) do
true →
:erlzmq.send(frontend, msg, [:sndmore])
false →
:erlzmq.send(frontend, msg)
end
end
loop(frontend, backend)
end

That example (rrbroker.exs) seems to work. But, I don’t know how it’s being done underneath in erlzmq (erlzmq2). Looks hopeful, though.