Both Zettlr and Typora are
Markdown plain-text editors.
Zettlr
Zettlr is a general-purpose open-source Markdown note-taking app. Fast, simple, and versatile.
Typora
Typora is a minimal Markdown writing and note-taking app. Its signature trick is the live preview of Markdown.
Fan of Markdown note-taking apps? 🤔
Maybe Paper is what you're looking for.