hi welcome.
i’ve never heard of a zidoo z9x before. the big question is if it can direct play or direct stream a 4k file. If it can, then you can use a low power nas. But if you ever need to transcode for an incopatible device (or low bandwidth connection) then you will need a good transcoding gpu and a nas killer will die.
nas killer 1.0 is quite old now. may want to look at a nas killer 4.0 or 5.0:
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if you think you may need to transcode, best budget option is to look at the intel igpu boxes.
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