I'm out the other side now so I wanted to share my personal experiences if someone comes across this thread in the future. Everyone is different but it can be helpful to know possibilities.
I experienced light fatigue but it came in waves. I didn't have my usual enthusiasm to leap to action at work and took things at a slower pace. While I did over 11k steps some days, I felt better on days I limited myself to 6-8k steps.
After the first few sessions I got help with the driving so I only had to drive half the journey each day. It gave me a chance to rest for an hour and not have to concentrate between getting zapped and working.
Doing zaps during the week and then working 9-5 on a few of the weekends was a bit tough - in hindsight I would have asked to swap shifts so I would have had a rest from both work and zaps.
I made sure to stay extra hydrated especially as we went through a heatwave with days over 40C and I was working outside for part of the day.
I went to sleep earlier than usual and slept longer. On my days off work I took short afternoon naps.
For the duration I skipped doing anything other than getting zapped, work, eat and sleep. I'd made sure to stock the kitchen cupboards before hand so I only had to pick up a bit of fresh fruit and veg from a small shop a few times rather than doing a big shop.
5 days later I'm still feeling a bit tired but it should start easing off soon.