Swappiness is set to 150 out of the box

[cscs]

To take from man udev

The udev rules are read from the files located in the system rules directories /usr/lib/udev/rules.d and /usr/local/lib/udev/rules.d, the volatile runtime directory
/run/udev/rules.d and the local administration directory /etc/udev/rules.d. All rules files are collectively sorted and processed in lexical order, regardless of the
directories in which they live. However, files with identical filenames replace each other. Files in /etc/ have the highest priority, files in /run/ take precedence over files
with the same name under /usr/.

@Kalzi

Why does it still show 150 even after changing it to 180 in 30-zram.conf and rebooting?

cat /proc/sys/vm/swappiness

150

So I dont know how this would be true - even if 30 was used instead of 99.
Unless you mean you edited the /usr/lib/udev/rules.d/30-zram.rules after copying it to /etc/ (leaving the new /etc/udev/rules.d/99-zram.rules file as-is) .. if so then that would explain it. We wanted to edit the /etc/udev/rules.d/99-zram.rules file after creating it.

Double check?

cat /etc/udev/rules.d/99-zram.rules