Customers may have a variety of reasons to show zero price lines
1. They are consuming the hours bank and need to show progress against the hour bank on an invoice without billing the customer again
2. They do pro-bono work for the client but want to display the hours that they are giving credit to the customer to prove they have provided the work
3. They have timesheet lines of non-billable resources that need to be shown on an invoice to prove the work has been done.
Kim Bateson
From your request # 2 and 3 are in the August 2020 Release.
Hour Banks are excluded from invoicing as they are in the hour bank. There is another idea for a report for this that we are considering.