I tried to install Ubuntu 18.04 on Acer Aspire 4720Z but failed. My installaition stuck in the very beginning on bootlogo. I updated BIOS on latest version form Acer site. Previously I successfully instaled Ubuntu 16.04 in that laptop.
Ubuntu 18.04 is a 64bit OS and does not support 32bit computers like Acer aspier 4720Z. Ubuntu MATE 18.04 still works on 32bit computers. You can download it at ubuntu-mate.org