My use case:  Create a new Invoice, using fields in the Potentials module in Zoho CRM - I want a button to do this.  (Yes - I appreciate that this is not a normal use case, we have a simplified implementation of CRM that does not use Sales Orders etc)

Problem - it's pretty straightforward to populate normal fields, I came unstuck with lookups.

My lessons:

1.  You need to make sure you use the API Name when referencing the field (found in the Setup -> Developer Space -> APIs -> CRM API).

2.  You need to get the ID for the lookup you are populating 

(I could have saved a lot of time if I'd found this info in the documentation or online forums.  In the end, I got my help via a support request.  The documentation might not be perfect, but the Zoho support for Deluge is really helpful!)

Example:

Creating a button in Potentials to create a new Invoice, using a deluge script...  (we call our Potentials module 'Projects')

Key items from my Deluge:

pId

p_AccountName = ifnull(respMap.get("Account_Name"),"").get("id");  // gets the id for the Account

paramap = Map();   // create map translation for fields to go into Invoice

paramap.put("Subject",'INV ' + respMap.get("Deal_Name"));  // example of straightforward field mapping{ie paramap.put(to field using API Name in Invoice, from field using API Name in Potential)

paramap.put("Account_Name",p_AccountName);  // field mapping for Account_Name (my API Name for Account Name) 

paramap.put("Contact_Name",p_CustomerName);  // field mapping for Contact_Name (my API Name for Contact Name) 

paramap.put("Related_Project",pId);  // field mapping for Related_Project (my API Name for Potential Name) 

paramap.put("Status",'Created');  // sets Status to 'Created'

// further field mappings (making sure I use API Names)

createResp = zoho.crm.create("Invoices",paramap);  // create invoice

I trust this helps!