Hard to understand CRM <-> Invoice!

Hard to understand CRM <-> Invoice!

Hello @all!

I am noob, so please bear with me.

I just started to use Zoho and the funcionality is overwhelming. I started with the CRM and begun to open clients, change Invoice look and feel, creating invoices and products... bear in mind, all at the CRM application.

After some while I started to understand, that, for proper invoicing, I should use the "Invoice" module instead of the CRM, so I wanted to take over the created invoices. Hm... I can´t figure it out!

Then I searched, how I could manage to get all the products (CRM) into the items (invoice application), hm... I can´t figure it out again!

The only thing that worked, was to pass over the clients data.

As I have to use credit notes, I need the invoicing application. So why are there different Invoicing / Products possibilities which even do not correspond to each other? How may I use the already entered data and custom fields for the both sides?

It seem some how confusing to have the same module on two different applications and it seems to me, that they do not work together and create redundancy which really may get a problem in the future!

Is there any logical explication and how do I migrate from CRM to Invoice?