I took a closer look at the boots and saw there is a seam on a perfect hight to make them ankle boots! So let the upcycling begin.
Shafts looking really bad
First I cut the shafts off being very careful not to cut the lining. I cut the zipper and the lining shorter.
The I trimmed the lining and zipper about 1cm above the seam. I secured the lining and zipper with pins...
... and started sewing by hand. I broke one needle since I started with too thin needle. :)