How hardcore is the workout? How do you feel doing it?
If you’re not a elite athlete min/maxing and you feel fine, do whatever feels good.
For example. I have learned that I can do a full lifting workout or run <= 4 miles up to 24-36 hours into a fast just fine. I cannot do a hard running running workout 4+ miles > 24 hours into a fast without it being a bad time.
There is some limited evidence that taking HMB while fasting limits muscle loss, so I also do that (yes, it might have a few cals, I don’t care)