I tried another time yesterday (your today ;-) I think) but still gives me one drive at 8Gb not allocated, the other one not recognized.
I repeated the procedure for both the 4 tb drives: I formatted in GPT mode and get two 3761,... Gb drives.
I formatted in NTFS mode and at present it is copying the huge amount of files...
I think the problem will not represent again if I use the USB plugs. This way however it will cost 22 hours for the main copying process instead of 7,8 hours with e-sata plugs. Thank you anyway for your answer.