Integrate AWS Trusted Advisor with AWS Config to set up a custom Config rule that triggers an AWS Lambda function. This function would then send notifications to an Amazon SNS topic, which is subscribed to by both the Slack channel and the shared email inbox.

Utilize Amazon EventBridge to track AWS Health events related to maintenance. Configure these events to trigger an Amazon SNS topic, which in turn invokes an AWS Lambda function to forward the notifications to the designated Slack channel and shared email inbox.

Develop an AWS Lambda function specifically for sending EC2 maintenance notifications to the Slack channel and shared email inbox. Use Amazon CloudWatch metrics to monitor EC2 health events and set up a CloudWatch alarm to activate the Lambda function upon receiving a maintenance notification.

Set up AWS Support integration with AWS CloudTrail to create a CloudTrail lookup event. This event would trigger an AWS Lambda function to relay EC2 maintenance notifications to an Amazon SNS topic, which is configured to send messages to the Slack channel and shared email inbox.