To reference a work with two corporate authors, you would use the same process as with multiple individuals, for example:
Australian Government Productivity Commission & New Zealand Productivity Commission. (2012). Strengthening trans-Tasman economic relations. https://www.pc.gov.au/inquiries/completed/australia-new-zealand/report
Note how you separate the two authors with an ampersand ("&") symbol.
In the text, this reference would read (Australian Government Productivity Commission & New Zealand Productivity Commission, 2012).
You could also abbreviate this reference if you are going to be referring to it multiple times. See link below for more information.
