Both ISO/IEC 17025:20117 and ISO/IEC 17020:2012 are conformity assessment standards. They have common requirements and are structured in the same way in terms of Management requirements, General, Structural, Resource and Process requirements. If the responsibility for the management systems is with the same person, or group of people; it should be straight forward to have common processes and procedures. You would need to integrate the laboratory activities into the current processes, for example complaints, corrective actions. I suggest you look at the responsibilities and perform a gap assessment on what is required to “add” or build on to your existing management system. Perform a risk and benefit analysis of merging the two systems.