I stopped the Zygard EB early as well, other game priorities took precedence.
For the Diance EB- I am currently using MegaMawile, Jirachi, Klinklang, and Dialga. I already have Diance and the stone, I could really use the Candies to boost MegaRayquazza since I just cleared main stage 300. MegaRayquazza is beast!
I will probably stop the Diance EB after there are no more chances to get candies- (haven't looked at the prizing list), I do not want to spend to much resources on the EB.
I was able to mange a score of 70295 on the Garchomp Challenge, since I already had the stone it was good to get a candy and a RML.
Next week though, the MCHarX comp is going to be good, since I missed the last time it was around so it will be nice to have that stone.