We have a requirement where company A is merged with company B, they both use HFM

We have a requirement where company A is merged with company B, they both use HFM application and on diffent instances. Repoting struture followed by A is IFRS and used by B is USGAAP. Now A will be the primary app where we will be adding content of B but primary reporting needs to be in USGAAP and also IFRS should work in parallel. Just wanted to check if someone worked on this sort of scenarios and what challanges can we face. And approch to follow for this sort of requirement.