AWS lambda with large size library

Have you tried using a Container image for Lambda - those can be up to 10 GB in size.

You have several limitations for AWS lambda https://docs.aws.amazon.com/lambda/latest/dg/gettingstarted-limits.html

If your zip file is bigger that 50 MB and you can made a direct upload, upload de file to S3 and deploy from there. https://docs.aws.amazon.com/lambda/latest/dg/configuration-function-zip.html

Another option is use lambda layers. Package rembg as layer and you only need to upload the custom code.

If you are hitting the 250 MB limit for unzipped source code (including dependencies and lambdas), use a lambda container instead of .zip