I faced this issue before and I tried many things ,Then I found Zip Handling module ,Through this module you can add a list of documents to .zip file and the below is the marketplace link :
Please check the below example :
take a look at this i think it may help you
you handle it by the following steps:
- create a sub microflow which contains your file as a parameter, and add download activity with your file as input.
- create a nanoflow contains your files list.
- add a loop to iterate over your files list.
- add the previous sub microflow to the loop, and let the iterator file as input for the sub microflow.
you should have something like this in your nanoflow
The following appstore widget will help you to download multiple files
and also the following forum answer will guide to achieive it