Update a field in Contacts from a custom module

Update a field in Contacts from a custom module

Every time a new entry is recorded in a special module, I would like a specific field in the associated contact (through the email) to be updated. 

The field in the costum module "Vingo Rides" is "RideStartTime"
The field to update in Contacts is "Last Ride Date"

I tweaked an existing function to get to this :
custinfo = zoho.crm.getRecordById("Vingo_Ride",custid);
ctime = custinfo.get("RideStartTime");
relcont = zoho.crm.searchRecords("Contacts","(Email:equals:" + email + ")");
if(relcont.size() > 0)
{
contid = relcont.get(0).get("id");
update = zoho.crm.updateRecord("Contacts",contid,{"Last_Ride_date":ctime.toDate()});
update1 = zoho.crm.updateRecord("Vingo_Ride",custid,{"Contacts_Name":contid});
}

However, I keep getting error messages (please see attachment) when I run the workflow.

What am I doing wrong?

Thank you!