The simplest way to import RIS file to Zotero at the exact collection - use import from Clipboard. Open RIS file, Ctrl+A, Ctrl+C (select all and copy to Clipboard) Go to Zotero, navigate to collection, Ctrl+Shift+Alt+I (or Menu->File->Import from Clipboard)
Upgrade Storage
Open RIS file, Ctrl+A, Ctrl+C (select all and copy to Clipboard)
Go to Zotero, navigate to collection, Ctrl+Shift+Alt+I (or Menu->File->Import from Clipboard)
Best regards,
Andrey