ISO 13485 and AS NZS 3551 are both dealing with medical devices, but they are very different.
AS NZS 3551 outlines procedures required to develop management programs for medical equipment. These include protocols and procedures for procurement, acceptance, maintenance activities throughout the service life of the medical equipment, and finally disposal of medical equipment. This Standard applies whether the medical equipment is owned by the responsible organization, privately owned, on loan, on hire, on trial or donated, and includes medical equipment provided by a responsible organization as part of a pool of medical equipment for hire.
ISO 13485 specifies requirements for a quality management system where an organization needs to demonstrate its ability to provide medical devices and related services that consistently meet customer and applicable regulatory requirements. Such organizations can be involved in one or more stages of the life-cycle, including design and development, production, storage and distribution, installation, or servicing of a medical device and design and development or provision of associated activities (e.g. technical support). This International Standard can also be used by suppliers or external parties that provide product, including quality management system-related services to such organizations.