When comparing TOAST UI Editor vs Zettlr, the Slant community recommends TOAST UI Editor for most people. In the question“What is the best WYSIWYG Markdown editor?” TOAST UI Editor is ranked 1st while Zettlr is ranked 9th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Easy to use
Pro Open source
Pro Visual Studio Code extension
UNOTES - Visual Studio Code Extension uses TOAST UI Editor.
Pro Focuses on writers
While many Markdown editors don't offer specific support for a certain type of workflow, or offer features for scientific workflows only, Zettlr offers features that help the writing process of journalists or researchers in the arts and humanities. It's a lot more text-focused than most editors.
Pro Citation support
While it supports a diverse range of syntax (chart, easy image insert, etc.) found in other editors, the great citation support made it possible to write real articles. Citation from Zotero and Mendeley can be inserted easily which is a huge plus.
Pro Almost perfect
This is the best option, still not perfect, there are some bugs like creating / editing tables and resizing images, but the PROS destroy the CONS, easy quotes, WYSIWYM , attachments tab (supports attaching and opening links to any file), table of contents, TAGs, easy hyperlink between files (same as citations), export to many formats (like Word, HTML5, PDF)...
Pro Renders math in-place through KaTex
Cons
Con Does not automatically add http or https for url yet
This can be a big deal for some apps. The project team said they are going to fix this issue in 2020.
Con Source code highlighting is not working by default
Con Obtrusive, like someone WITH CAPS LOCK ON
Too loud, too much going on, and definitely an in-your-face sort of feeling.