Step 1. Go to zombies sign in as guest with second controller
Step 2. Go to custom games and hover over map
Step 3. 1st Controller Hover over leave
Step 4. 2nd controller Hit leave as soon as you hit leave hit circle on first controller you should sign out
Step 5. 1st controller sign in with account you want your rank to be
Step 6. 1st controller sign out and sign back in as real account and bam you got the rank you wanted