With these kinds of zombie jobs, you will need to file a support ticket, so that GCP support can force the job update, or force the job to terminate.
Please let me know if you are having any problems filing a support ticket and getting this figured out.
If you don't have a Support Subscription, and you issue is a Zombie job stuck on update, you can also file a private issue here: https://issuetracker.google.com/issues/new?component=491268
In the issue, mention your project and Job ID, so we can find the job easily.
But please do not file other support issues there, and use the normal support channels if you can.