You have a Google Cloud Platform account with access to both production and development projects.

You can create two configurations – one for the development project and another for the production project. And you do that by running “gcloud config configurations create” command.

https://cloud.google.com/sdk/gcloud/reference/config/configurations/create

In your custom script, you can load these configurations one at a time and execute gcloud compute instances list to list Google Compute Engine instances in the project that is active in the gcloud configuration.

Ref: https://cloud.google.com/sdk/gcloud/reference/compute/instances/list

Once you have this information, you can export it in a suitable format to a suitable target e.g. export as CSV or export to Cloud Storage/BigQuery/SQL, etc