I use LavaFox Purple, and reviewed that , but this part applies to every ZigBoom Theme.
LavaFox/BlacFox are Awesome Themes, that Mozilla's "Chrome" Quantum (Firefox v57+) have abandoned, alongside many of mu must have extensions. Thing is they are must have's Quantum isn't, so I ditched it, for Pale Moon.
This gives some info on keeping your Zigboom Theme.
ZigBoom's Facebook Post
-=< The Future of Firefox Themes >=-
Mozilla announced that Firefox will stop supporting themes when version 57 hits the official channel. Since there are no signs of new theme API, Mozilla is disabling all 3rd party themes on the next version bump.
Our themes LavaFox & BlackFox will keep supporting other Firefox Forks, mainly Waterfox & Pale Moon.
The latest theme versions are fully compatible with Waterfox and will keep updating.
Pale Moon is supported with themes version 2.5.0. Special version will be uploaded to Pale Moon's add-on site as soon as possible.
All the themes are available here: https://addons.mozilla.org/en-US/firefox/user/4710003/
Previous Versions Links
So that answers my future concerns, and only leaves the Pale Moon's current v2.5.0 requirement.
I've worked out the Previous versions link is same format used for the Extensions.
You Simply add, the next line to any Add-ons base page address
BlackFox V2 (Main Page Address)
Adding the versions section, make sure to add a leading "/" if your Firefox address is missing it
BlackFox V2 Version History
Install v2.5.0, for Pale Moon until Zigboom can provide the custom Pale Moon Themes, which will be posted here