The ZX uses a different rear suspension than the 77 280Z.
I have oil-KYB's on my 73, but am replacing them with Tokico Illuminas this summer, as they control better.
A cheaper alternative is the regular Tokico Gas Strut cartridge, about 60$ a corner. They control better than the "Racing" KYB Oil units did new...
And that's about half as stiff as an Illumina can get set on "5".