First, try to do this wipe setup:
2. remove /usr/local/zend
3. remove user zend
4. remove Apache if you don't have any important settings, rename / remove /etc/apache2 and any leftover settings
5. apt-get update, apt-get autoremove, apt-get autoclean, apt-get install -f (probably will do nothing)
6. install Zend Server using the linux installer for ZS 9.0.1 (or apt-get install zend-server-php-7.0 for existing repo)
7. check http://127.0.0.1:10081
8. if something is still not working, you can open a support ticket on support.zend.com, link back to this forum topic, and provide a support tool dump from /usr/local/zend/bin/support_tool.sh with the problem description, so we can assist with some offline facts.