When comparing Zim Wiki w/ journal plugin vs Zettlr, the Slant community recommends Zim Wiki w/ journal plugin for most people. In the question“What is the best single-user wiki?” Zim Wiki w/ journal plugin is ranked 12th while Zettlr is ranked 16th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Plain text file structure
Pro Write a journal when you want
There are 3 options for writing frequencies: daily, weekly, or monthly. It's great that you can configure it, because not everybody writes a daily journal but because there are set days, you will be more motivated to actually write in your journal on those set days.
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 Obtrusive, like someone WITH CAPS LOCK ON
Too loud, too much going on, and definitely an in-your-face sort of feeling.