zoho crm functionality vs stand alone modules

zoho crm functionality vs stand alone modules

When I first began using zoho I purchased separate modules such as zoho docs and zoho invoice. then I purchased zoho crm and now I wanted to bring over the docs to the crm docs and use the invoices under crm. however, I noticed that much of the functionality that were in the individual modules are lost in crm.
 
Is this truly the case or am I missing something? If someone can give me some best practice guideline about how to get this all to work well together I would appreciate it as I would like to put everything under one roof if at all possible.