These extend the zuca cart handle 30mm away from the frame at the top, and ~ 18-20mm away from the bottom. This allows for more of the seat to be used. You can use just the top extender, if you prefer the handle to angle back from the cart more.

I printed with 6 walls and 65% infill with PLA.  Initial version had 6mm holes, which are very snug for M6 screws - this version has 6.5mm holes instead.