Hello
There is no specific google guideline that talks about migrating Route 53 public records to gcp. Make sure you followed this article about migrating records to gcp. The issue may or may nor be related to the zone file format.
It is important to mention that Google Groups is a discussion forum on GCP products not a site to troubleshoot customer specific issues. So you should be posting this question on Stack or Serverfault where the community members can help you to troubleshoot this issue.You can also reach out to Google Cloud Platform support. In that case, It’s always helpful if you share the exact command you are running as well as results, errors and the config file. While doing so make sure you are not sharing any sensitive information.
Thanks