He used a carbide bit. They will drill through taps, ez-outs, and hardened allen wrenches, been there, done that. But they are expensive and chip easy.
And like I said, if he broke a ez-out off trying to get it out, I do not think the 3 or 4 little spindly legs of a extractor are going to get it out.
Besides the extraction welding rod idea, the only other idea is get a hole started as close to the center as you can get it, and if you have larger sizes of carbide bits, slowly open the hole up, till you have cut most of the tap out, and are left with little bits and pieces that can be picked out of the threads of the block.
And like I said, if he broke a ez-out off trying to get it out, I do not think the 3 or 4 little spindly legs of a extractor are going to get it out.
Besides the extraction welding rod idea, the only other idea is get a hole started as close to the center as you can get it, and if you have larger sizes of carbide bits, slowly open the hole up, till you have cut most of the tap out, and are left with little bits and pieces that can be picked out of the threads of the block.