Multiple Companies

Multiple Companies

We are looking to use Zoho (Professional Edition)
 
My issue is Currently I have one resource who will work on a set of accounts.
 
Next week I am due to also get another set of accounts that I want to assign to another resource that I have.
 
How do I keep seperate the two users. I want to be a power administrator for both but I dont want them to be able to see each others.
 
We aren't using ZOHO as a traditional Sales leads and conversions tool but more as a tool to make notes and create actions when talking to clients about Ledger Issues, basically chasing up Debtors Payments.
 
Any ideas how I can structure this ?
 
Many thanks,