What are some alternatives?
When comparing POEditor and Zanata, you can also consider the following products
Crowdin - Localize your product in a seamless way
Transifex - Transifex makes it easy to collect, translate and deliver digital content, web and mobile apps in multiple languages. Localization for agile teams.
Weblate - Weblate is a free web-based translation management system.
Poedit - Poedit translations editor. The best way to translate apps and sites.
Smartling - Website localization & translation
Pootle - Multiple file formats.