Several estimates for monthly invoice?

Several estimates for monthly invoice?

Good night,

First, thanks for Zoho. There s many details that we are looking for, but it s a good system.

I have a neccesitie, I send different estimates along the month to my clients, BUT we only send one invoice monthly,
At the end of the month, how can I join all the estimates in ONE, to convert in a unique invoice?

Thanks in advance,