Would they even be possible in ZH engine ?
Just to make it clear, I am not proposing anything,
imo Cloning would be too much even for a someone like Alexandr,
just wanted to know would it be possible to work somehow in ZH environment
as it did in Red Alert 2 and Yuri's Revenge ?

No, it's not possible exactly like that. However, it might be possible in at least a similar way.

You know how Red Guards are produced in pairs? It may be possible to make the Cloning Vats structure fire a status effect with map-range, which changes the Command Set of the production structures to make every unit build button turn into the 2-person version. But this wouldn't be bug-free (queue'd units would be single-unit until the "true" two-unit production ones are being done).

It would be easier to have the Cloning Vats as a purely visual add-on to an existing structure instead. Or alternatively, have it as an alternative production structure which produces everything in doubles (there was a mod that turning ZH in YR which did exactly that).

Red Guard infantry count as clones?

...No.

In terms of game mechanics, yes, because they are produced in groups of two as SoraZ described. In terms of story, they are obviously not clones because human cloning technology was never hinted at in any canon material. They only spawn in twos as a way of highlighting the massive amount of troops that China has at its disposal. All other factions produce single infantrymen, the spam faction with the manpower advantage produces the smallest tactical unit, which is a two-man fire and manoeuvre team/battle pair, as a way of translating that aspect of their lore into tangible gameplay.

(delete)

he just said its possible code wise, and that it will NEVER happen in game or be official

EDIT: Nice sneaky delete