Maybe....see if you can get into Disk Utility from the Mountain Lion Installer. You may have to move the mouse to the top center of the screen and OS X Tools should show up. Maybe that's a Sierra/High Sierra thing. Quit the installer. You should still be able to get into Disk Utility, should be at the top of the screen.....going from memory here....choose your disk on the left hand side. If it doesn't show up, make sure that "Show all disks" is checked off. and click on the button on the top left. You have erased it, which is Ok. But you need to format it as well, MacOS Journaled (Extended), and GUID on. Give it a name, and then choose erase again. This should create a partition on your hard drive (You only need 1 usually), and from there, you can quit Disk Utility and try again to install Mountain Lion
hope this helps a bit
John B