If we attach one Mathcad 15 file with extantion .xmcdz there is no need to archive it one more...
Name.mcd -> Name.zip
Name.xmcd -> Name.zip
but
Name.xmcdz -> Name.xmcdz
In this case (Name.xmcdz -> Name.xmcdz) we can do references on this file from Mathcad-sheets (Mathcad cloud functions IT)