You're a student. Your life is busy. You need Zotero because your time is valuable. Zotero saves time in several ways.
Zotero is free, open-source software. It doesn't cost you anything to download and use it.
The only costs associated with using Zotero relate to storage costs. When you sign up for a free, online Zotero account, you get a complimentary 300MB of online storage. Should you ever need to upgrade your storage, Zotero offers reasonably priced storage options.