Pino transport: apply ECS format only to Elasticsearch target

I have this Pino transport with two targets:

const transport = pino.transport({
  targets: [
    { target: 'pino-elasticsearch', options: { /* ... */ } },
    { target: 'pino-pretty', options: { /* ... */ } },
  ],
});

And the logger:

import ecsFormat from '@elastic/ecs-pino-format';

const logger = pino(
  {
    level: 'info',
    ...ecsFormat(),
  },
  transport
);

Problems:

1. Using ...ecsFormat() with both targets stops logging completely. It works if I remove one target or remove ecsFormat().
2. I only want ECS format for Elasticsearch logs, not console logs. Examples I found apply it globally.

Question: How can I apply ECS formatting only to the Elasticsearch target?