Hello Pascal_User,
Welcome to the forum.
I have no problem installing ZeosDBO package on my Lazarus 1.8.0 64-bit Ubuntu 17.04 using Online Package Manager.
Online Package Manager is a handy tool that can help you automatically downloading necessary files and installing packages. If you're using Lazarus 1.8.0, you can find it on:
Lazarus main menu > Package > Online Package Manager