I haven't seen very many posts on this forum about zinc rot and my collector and operator friends have not complained about it either. I think that this problem is rare. Many people on this forum have engines that are 20 plus years old.
The only zinc rot problems that I have had was with a few trucks and couplers. They can be replaced. I am sorry that you have an engine with the problem but I don't think you will need to worry about most of the engines that you purchase will fall apart.
The electronics are another story. There is usually a way to fix most electronic problems.
NH Joe