Reddit reviews Mazinger Z TV Series Part 2

Honestly, you're not missing too much. While it is fascinating to see the origins of super robot anime, it's poorly scripted, it drags HARD through most of it, and it's mostly just monster-of-the-week with very few episodes ever advancing the overall plot. There's probably a way to condense the series down to 15-20 episodes without skipping anything of note.

That being said, Mazinger Z is licensed in the US by Discotek Media, and not (legally) available for streaming. You are unlikely to find it used for cheaper than $80 for both box sets together.

DVD Box 1

DVD Box 2

Yeah, Vol 2 came out a few years ago. Its out of stock on Amazon Maybe its out of print?