A flush hollow core could potentially be split, most I've seen are nothing more than stressed skin construction with little more than a 1-1/2" frame with cardboard battens within the field of the panel. Skillsaw with rip guide to slit the door frame, a handsaw could be used to finish off any blocking installed for hardware. Then gently separating the skin from the carboard battens.
Six panel (or similar) molded hardboard would be tough.... although some stressed skin elements exist, the molded decor of panels might be pressed/glued too tight together internally to split. Potential again to use hand saw if door can be initially split with skillsaw then pry apart to see if panel sections will release.
A real wood door?...... might consider just approximating existing doors using applied trims to a piece of plywood or mdf.