How to make an USB coected, external Hard Drive (mechanical) to dual boot with Windows 10 Enterprise and Linux?

I have an USB 3 coected, 4Tb Segate Backup Plus Hard Disk. I want to create several partitions and dedicated two of them (≅126 Gb each), one for Windows 10 Enterprise (no home or pro), and other for Linux (any distro will do it but Ubuntu is preferred). I don't want to create a single partition that takes all the space for this. The unit will be coected to any computer so it can boot on either OS (dual boot).

I already tried [diskpart] but after creating the primary partition and trying to make it "active" a message is retued saying that it can not be make active. I check and utility called [wintousb] but it is not free for Windows 10 enterprise. The [GImageX] tool seems to need a single partition occupying the entire disk space, I need to devide the disk in several partitions.