Here’s how to list GCP instances with a specific service account.

gcloud compute instances list \
--project your-project-id \
--format="value(name,serviceAccounts[].email)" \
--filter="serviceAccounts.email=your-service-account@email.com AND name~\bwp"

I’m using filters to look for a specific service account, and any instance starting with ‘wp.’ \b means begins with.