There is no master if multiple nodes are running the same RAFT group you can write and read from all of them so yeah a load balancer should work well.
What is the value of --replicas flag that you are using to run Zero and how many Dgraph servers are you using? I can try and explain based on that.
You could add a constraint and keep it to only one of the nodes or you can run it on all of them, it depends on what you are looking for.