The instructions you’ll find elsewhere tell you to just twist the head of the shock absorber a quarter-turn to release it. That’ll probably work, although I think you’ll break the two locking clips that hold the head in place, after which you’re depending on friction to prevent the whole affair from shaking loose.
The head is the small bump visible inside the white bracket on the tub. The locking clips are the tabs inside the square shape just under the bracket. It’s obvious when you see it, if you know what you’re looking for.
The trick is to use a small screwdriver to pry the locking clips downward while twisting the head. This is impossibly awkward, but you can get one started, lever the other one out, and then both will suddenly slide free as the head turns.
If you’ve removed the three concrete tub weights, the tub will rise up as you release each shock absorber. Mind your fingers!