In the doc...

http://zohocrm.wiki.zoho.com/Setting-up-Field-level-Security.html

it says...

For example, "Sales Stage" and "Amount" fields in Potentials module may not be required for a person looking at customer support. Similarly, "Status" of the cases can be hidden for the users other than customer support persons.

But I can't untick "status" in "cases", it's greyed out.

Also "sub total", "grand total" in "invoices" is greyed out too which would be needed for a customer support/non-sales profile.