zelgius or LA Hector?

Yeah but why not just put both into your team?
Plus you are comparing an excelling amored red to an armored green.

They both serve somewhat different roles since they are different colors to begin with, but they'll both do amazing. If you have space for both go for it. LA Hector can deal with Reinhardt and Brave Lyn well, while Zelgius still gets ORKO by Reinhardt.

You’re comparing apples to oranges. Two entirely different units with only movement type to share, it’d be like asking if Ayra or Linde would be better for use.

To answer your question, they are both top tier units, it would be up to you which unit better suited your specific team needs.