It's incredibly hard to do. If the bibliography has DOIs, you can open the document in your browser and you should be able to pick up most items with DOIs via the toolbar icon, but otherwise parsing bibliographic data from formatted bibliographies is a major, largely unsolved challenge. See also here http://www.zotero.org/support/kb/importing_formatted_bibliographies
Doing this by hand can be accomplished surprisingly quickly. -In the Word document, copy the title of the journal article or book. -Paste that title in the regular google search field. (It may be a good idea to place the title within quotes.) You don't need to use Google Scholar for this. -In the search results find the item that resides on the publisher's website or on PubMed. -Open the link in FireFox. -If there is a zotero article or book icon in the URL bar, click it to download the item into your Zotero database. If not, look for a "download citation" link. RIS and BibTeX can be imported into Zotero.
If you have a reasonably fast Internet connection each title should take no more than 20-30 seconds. Unless you are a very fast and accurate typist this will save you a lot of time.
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See also here
http://www.zotero.org/support/kb/importing_formatted_bibliographies
-In the Word document, copy the title of the journal article or book.
-Paste that title in the regular google search field. (It may be a good idea to place the title within quotes.) You don't need to use Google Scholar for this.
-In the search results find the item that resides on the publisher's website or on PubMed.
-Open the link in FireFox.
-If there is a zotero article or book icon in the URL bar, click it to download the item into your Zotero database. If not, look for a "download citation" link. RIS and BibTeX can be imported into Zotero.
If you have a reasonably fast Internet connection each title should take no more than 20-30 seconds. Unless you are a very fast and accurate typist this will save you a lot of time.