Zotero allows you to collaborate with others by creating groups and building shared group libraries.
To create a group:
Group libraries:
Syncing, Collaboration, and Backup -- Zotero Groups:
https://www.zotero.org/support/groups
Watch this short video, from the Groups tab:
https://www.zotero.org/groups/
Options for organizing the items in your Zotero library include:
Collections
Tags
Related items
Sorting
Organizing Your Library and Taking Notes -- Collections and Tags:
https://www.zotero.org/support/collections_and_tags
Organizing Your Library and Taking Notes -- Related Items:
https://www.zotero.org/support/related
Organizing Your Library and Taking Notes -- Sorting:
https://www.zotero.org/support/sorting