Hi gundammk10,
Yum has several audit standards , which one you mean , I'll assume you mean food safety audit (FSA) ,
There is a difference in requirement for FSA Yum! audit and ISO 22000 since YUm is more following GFSI recognized certifications , however
you can do it ,I recommend before doing that to create a matrix between the two standards requirements , then according to this matrix you conduct the internal audit assuring you covered both requirements, also report them in different reports to assure you do not missed any requirement.
Make sure that there is some requirements are not the same for example fraud detailed assessment or food safety culture requirement .
So after you complete the matrix you will have a comparison between the both standards , go through the audit using this matrix as your internal checklist , for example Clause 11 (FSA ) Traceability in column A , clause 8.3 Traceability system in column B then findings in the column C and D receptively.
If the requirement is not clear for one standard or not required leave empty and noted as NA.
Finally you will have both audits in the same time column A and C there other is B and D which the the requirements and the evidences /non conformists.
This is regarding FSA , however QSA is different as it is quality system audit it can be performed with ISO 9001.
BR,
Ehab