custom module lookup

Hi, I'm new to Zoho and I have a question about inserting lookup field via API. Here is my XMLdata:

{...some other fields...}

<FL val="SEID">2123329000000110563(id of CustomModule2 instance)</FL>

<FL val="SEMODULE">CustomModule2</FL>

</row>

</CustomModule>

$ch = curl_init(" https://crm.zoho.com/crm/private/xml/CustomModule/insertRecords");

But after I run the program, custom module has been added successfully with all the correct fields but custom module2 lookup. The custom module2 lookup field shows blank.

Then I tried one more time with 2 standard modules: leads and contacts. I created a leads lookup in contacts. Then I did this:

xmlData=<Contacts>

<FL val="First Name">Bruce</FL>

<FL val="Last Name">Moreland</FL>

<FL val="SEMODULE">Leads</FL>

</row>

</Contacts>';

$ch = curl_init(" https://crm.zoho.com/crm/private/xml/Contacts/insertRecords");

And again it has been added successfully with correct first name and last name but leads lookup field is still blank. Did I make any mistake when adding lookup fields? Any advice and suggestions will be greatly appreciated!