Sharpshooter is predominantly about luck, if you attempt it enough times, you'll eventually get it.
As for Shrine of Zuma: imo, if you can get past level 9, you can beat level 12, the only difference between the 2 is that the balls move slightly quicker and it takes a bit longer to fill the gauge but you don't have any more different coloured balls to worry about.
The biggest tip I can give: (I might be wrong on the terminology as Luxor and Zuma use opposing terms) go for the chains (where you make one match, 2 match, 3 match etc, not the one where you make 1 match and the game makes more matches for you), this fills the gauge up WAY faster and will help towards both level completion and ace times.
That was the breakthrough I needed to master this game. I haven't gotten Son of Sun yet because I hate Gauntlet and haven't gotten Score Champion on the 360 version yet (have on the PC) but hopefully, this will help you. Practice makes perfect!
Good luck!
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