Whmcs Releezee connection

Hi im looking for a solution for my mini company.
I use whmcs for billing but it does not perform well on accounting.

So i use an other piece of web based software to to accounting but that also can do billing.

So i wanted to see if they could speak to eachother and keep eachother up to date, i would be able to use both or just one.

I can povideu a dev whmcs install and a test reeleezee account

I supose that whmcs would be leading if 100% integration between the two is not posible, but perhaps we can speak via phone or smth about that.