Back up a second.
/etc/bash.bashrc is the system-wide settings file for bash.
$HOME/.bashrc (often abbreviated as
~/.bashrc) has your user's personal settings.
~/.bashrc is read everytime you start a new shell (open a terminal) and so is
/etc/bash.bashrc, you don't need to copy anything from one to the other, both will be read.
So, if your system has no
~/.bashrc, all you need to do is create one and add the relevant line to it:
echo ". ~/z.sh" >> ~/.bashrc
. is an alias to bash's
source: source filename [arguments]
Execute commands from a file in the current shell.
Read and execute commands from FILENAME in the current shell.