How do I associate a lookup record in one module with the related module with the CRM API?

How do I associate a lookup record in one module with the related module with the CRM API?

I need to add a lead programmatically and have it be associated with a project all using the Zoho CRM API. Is this possible? My many attempts have failed. This is my JSON: 
{"data":[{"Company":"TestmanLaw",
"First_Name":"Testman4",
"Last_Name":"Tester2000",
"Email":"test@test.com",
"Lookup":{"id":"4213674000026968024"}}]}