alt Hacker NewsThe Nightmare Course [1], so named because someone with that skillset (developing zero-days) is a nightmare for security, not because the course itself is a nightmare, and Roppers Academy [2] are both good for learning how to reverse engineer software and look for vulnerabilities.
The nightmare course explicitly talks about how to use Ghidra.
1: https://guyinatuxedo.github.io 2: https://www.roppers.org
The first is certainly interesting, but it won't help you develop 0day. I would think of it like more of a collection of fun puzzles and esoterica. For example all the heap unliking/metadata attacks and House of X stuff is pretty antiquated. These will help you win ctfs but are certainly not a prerequisite or even all that relevant to contemporary vuln research. Most of the public research I see is probably at least a year behind the current meta (and I expect the public internet will only grow more quiet over time)