We can bulk retrieve invoices using:

https://www.zohoapis.com/books/v3/invoicesinvoices/... 

However, this does not include invoice details such as line items, etc.

To obtain invoice with details, we can call: 

https://www.zohoapis.com/books/v3/invoices/{id}

https://www.zoho.com/inventory/api/v1/invoices/#get-an-invoice

However, this is inefficient as only one ID can be passed in.

Is there an API to get invoice with details by passing multiple IDs?

For example, there is an API to retrieve multiple items by IDs:

API: https://books.zoho.com/api/v3/itemdetails?item_ids=item_id1,item_id2,...

Is there an equivalent API to get invoice with details by passing multiple IDs?

Is this on your roadmap?