For starters...AH-1Z has two Ge-700-401C engines, not just one, the early models of Cobras G/H/P/F had single engine later models like J/W and Z have two engines.
Also you do not summe up the shp of two engines, that is not how it works. Both engines only share the workload, but it does not summe up to the double of shp, workload stays the same and is shared between engines, even if you use 10 engines the shp stays the same only workload devides among the engines.
And the WZ-10,AH-1Z and AH-64E are very comparable, share similiar requirements and role of use and the technologies that are worked on also represent counterparts which most attack helicopters don't have only US/Russia and China share such technologies so far, with one minor development of Turkeys mildar radar, however the rest stay unique to those three countries of development of new technologies.
The AH-64 has a higher payload yes, but it has inferior range the AH-64E has range of 408km with its fuel tanks, not counting external or additional fuel tank (robby tank).