Ok, now I get the HDD working so... I'm not an expert but I think its a problem of power, I just get the HDD to be recognized by Zidoo with a hard drive docking station, HDD was recognized, so I tried again with SATA connection with the same HDD and again no way. I'm almost sure (I repeat, not an expert) via SATA the HDD has not enough power to be recognized by Zidoo (4tb and 2tb should need the same amount of "energy" but who knows...) , the HDD start to spin and you can hear it buzzing but not with enough "volume", its like a little buzzing, instead if you connect it via Docking station the buzzing is louder and appears in Zidoo explorer, ZDMZ, etc.... So I'm happy because at least I can use both HDD 4tb, but sad because I have to use an external docking station, I prefer SATA connection because I suppose its faster but sometimes its the way it is. Thanks and maybe some expert can check the SATA connection with an ammeter o whatever, or maybe in future firmwares send more electric power via SATA, anyway thanks.