I have an s3 bucket which has a large no of zip files having size in GBs. I need to calculate all zip files data length. I go through boto3 but didn't get it.
I am not sure if it can directly read zip file or not but I have a process-

Connect with the bucket.
Read zip files from the bucket folder (Let's say folder is Mydata).
Extract zip files to another folder named Extracteddata.
Read Extracteddata folder and do action on files.

Note: Nothing shouldn't download on local storage. All process goes on S3 to S3.
Any suggestions are appreciated.
This is not possible.
You can upload files to Amazon S3 and you can download files. You can query the list of objects and obtain metadata about the objects. However, Amazon S3 does not provide compute, such as zip compression/decompression.
You would need to write a program that:

Downloads the zip file
Extracts the files
Does actions on the files

This is probably best done on an Amazon EC2 instance, which would have low-latency access to Amazon S3. You could do it with an AWS Lambda function, but it has a limit of 500MB disk storage and 5 minutes of execution, which doesn't seem applicable to your situation.
If you are particularly clever, you might be able to download part of each zip file ('ranged get') and interpret the zipfile header to obtain a listing of the files and their sizes, thus avoiding having to download the whole file.
Read zip files from amazon s3 using boto3 and python