Zettlr is great for some things. It has a couple downsides relative to something like org-mode:
It doesn't have any real outliner capabilities. Not that everyone wants an outliner, but you get it with org-mode.
It doesn't work like a wiki. In other words, if you link to a file that doesn't exist, it just says the file doesn't exist. It's kind of annoying to have to create those files manually and then reopen the document so you can add a link, even worse if you've linked to several notes you want to create.
I use org-roam extensively and create many many tiny files. Usually I start writing in daily note and simply link to the file. Then when I have something substantial I move to the linked file (automatically created when linking first time) and write stuff here. I get backlinks simultaneously so it is pretty easy to follow my chain of thoughts.
It doesn't have any real outliner capabilities. Not that everyone wants an outliner, but you get it with org-mode.
It doesn't work like a wiki. In other words, if you link to a file that doesn't exist, it just says the file doesn't exist. It's kind of annoying to have to create those files manually and then reopen the document so you can add a link, even worse if you've linked to several notes you want to create.