Tell ZuluTrade that as of today, you will cease referring clients to them. Explain that if they do not clearly explain what is going on and when you will be getting your money within 10 business days, you will warn existing clients that if ZuluTrade won't pay you, they should have no confidence in ZuluTrade acting in an honest fashion with their funds.
And, don't just threaten. Go ahead and suspend any efforts to recruit new people to Zulu and start working on the email to current clients. Then, if nothing has improved in 10 days, send it.