I've heard PLL,DLL and SMD are often utilized in such situation,but I'm not sure is it possible for a Phase Detector achieve the zero phase difference when the loop is locked. If it's possible what technique must be used?
In order to get rid of clock skew, I think the best solution is to use DLLs . I don' know a better method. However in order to minimize the skew of the DLL make sure to eliminate the deadzone. Also , minimize the charge pump mismatch.
your question is not clear. If you have eg 2 outputs on different side of IC and want them to switch with 0 skew no PLL will help you. You need to do a proper layout to have the clock path as symetrical as possible.
If you want clock in phase with input clock - PLL will work