Yes, you can.
When you create an invoice, Zoho Books will prompt all the unbilled expenses associated to the contact (as shown in the image below). You can choose to add the expenses to the invoice right there. You can select and add only the expenses you want to associate with that invoice, the remainder of the expenses will remain and will be similarly prompted the next time you select that particular contact to invoice.
These expenses are now added to the invoice as a separate item.