You cannot directly copy-and-paste existing bibliographies into Zotero. You have several options for getting items from your pre-Zotero bibliographies into your Zotero for future use:
Examples of the types of item Zotero can cite in APA Style and what data to enter into each field.
Examples of the types of item Zotero can cite in Chicago Style and what data to enter into each field.
From York University. A fairly comprehensive series of videos on how to use Zotero.
"...a variant of the well-known Zotero reference manager that adds support for legal and multilingual research and writing." You can use this unofficial version if you are already familiar with Zotero, however, the future development of this variant may not directly follow with upgrades to Zotero itself. Instructions to setup the multilingual fields.
A bibliographic reference manager for gathering and organization citation information. An MS Word plugin can perform the cite-as-you-write function. Firefox, Chrome, and Safari plugins assist with gathering bibliographic information while researching online. Generates bibliographies in various citation styles with one click.
A copy-paste converter that allows you to turn old/existing bibliographies into a file that can be imported into Zoter. Start by pasting into 1. Parse
