We use the API documentation to figure out how we should format our url within the invokeurl. Look at our code below and test out your function!
relatedTasks = zoho.crm.getRelatedRecords("Tasks","Deals",deal_ID);
info relatedTasks;
info relatedTasks.size();
for each task in relatedTasks
{
response = invokeurl
[
url :"https://www.zohoapis.com/crm/v3/Tasks/" + task.get("id")
type :DELETE
connection:"deletetasks"
];
info response;
}