If you don’t yet have the potion for Rainbow Bubbles, you can play earlier levels to earn 130 stars and then get busy using the rainbow bubble potion.
Clear at least a one bubble hole at the end of both rows of black bubbles(strategy picture 1). Then you have small openings to shoot at the upper bubbles to get the lower black rows to fall into the Cauldrons.
After managing to pop bubbles above the lower black rows at level 95, you need to be quite patient, trying to burst down the clusters of infected Bubbles, doom skulls and some crystals(strategy picture 2).
If you want even more guiding, please watch this videos. :)
3 Star video by the Blogging Witches (that would be the nickname for us. ;-))
It is the beginning of level 41 that is the problematic part. If possible, you might want to try focusing on clearing one side of the Doom Skull Bubbles first. It probably does not help you drop the big triangle of black bubbles alone, but helps your aiming a lot.
The Charm of Precision comes in really handy at this level. With over hundreds of games ahead, this is a good time to get it.