Updated to support each of the difficulties in BO4 (Casual, Normal, Hardcore, and Realistic). Note that only zombie health is affected and that you must enter a Campaign mission first with that difficulty selected because the console command is read-only apparently.

Compatible with Black Ops 1 and Black Ops 2.

Apologizes for re-posting, my previous post could not be edited.

Compatible with Black Ops 1 and Black Ops 2.

Overrides the default zombie health calculation with the one from Black Ops 4.

Click this link for the most up-to-date version, installation instructions, change notes, issues, etc.
https://gist.github.com/835a0e5aca5402f8fa24fe2812a6c5c9.git

Uses the zombies per wave calculation from Black Ops Cold War.

Click this link for the most up-to-date version, installation instructions, change notes, issues, etc.
https://gist.github.com/4224227766c9eed2112cbde0f66cc4d3.git