For the purpose of combo requirement, does a multiple copy retain it's attack zone after resolving or it become a blank face down card after resolving?

Say i have an mid attack with multiple 1, i play this attack, add the multiple, resolve them both. After that, if i play an attack which has combo E ( mid attack, mid attack ) can i play the combo E ?

The simple answer is yes.

retains zone, but not "type".

i.e.a multiple of spinning demon is low, but not a kick. (never was)

a multiple of DFK is not a throw (after it resolves).

HTH