I have implemented it in Mandelbulb, it's very hard to get a realistic terrain "with mountains" with a good detail level.
I tried hard, but the most decent result was this.
It looks somewhat like a "rose" - i think because you strongly rely on radius for the noise (length(z)*2.33 ... 2.33 is a lot).
The worst defect is that amplitude varies without a lower limit so if it's like 0.1 after some its it goes to 0.
this means, too low amplitude for higher its... So after 5-6 iters you don't get more details even if you use more iters
I use Mojoworld Pro its a terrain generator using fractal design elements. Your result looks similar to my Voronoi Volumetrics landscape.
The nearest to any reasonable looking terrain Ive managed with MB3D is this....
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............................................}