What are some alternatives?
When comparing Word Online and Zeplin, you can also consider the following products
Apache OpenOffice Writer - Open-source word processor of the Apache OpenOffice suite.
Invision - Prototyping and collaboration for design teams
LibreOffice - Writer - Open-source cross-platform word processor.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Google Drive - Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
Framer - Bring your designs to life.