Remodeling a bathroom shower. Replacing all tile, including tile floor in shower. What is best way to remove tile from existing mud base (built on concrete slab in recessed 4X5 depression). Possible to just remove tile and install new tile over existing mud base? Have removed hardiboard and tile on walls.

Going to be difficult. Only real way is to chip it out.

OK, thanks! Expected a challenge... On another Q: Looking at the Kerdi system of preparing a shower area, once tile is removed from existing mud base, can one just smooth out the surface with thinset and place Kerdi membrane down or would it be necessary to completely remove the existing base and build a new one?

Look at the Kerdi (schluter) website for details. I do not do this type of involved work with sloped floors and drains, I do not want the liability for leaks. Tile on flat floors, lot easier.