Execute tests based on different tags

I want to run tests which have tags either X OR Z , but the command which I was using can run only those tests which have tags both X AND Z :
cmd.exe /C testrunner.bat -r -j "-fC:/Reports" "-RProject Report" "-Edefault" "-TTestCase X,Y" "C:\Dummy.xml"

in that way my purpose won't solve.

I got one solution to run tests that have tags either X OR Z  by running the project two times: 
testrunner.bat -r "-RProject Report" -EDefault "-TTestCase X" ".......\XYZ\xyz.xml" testrunner.bat -r "-RProject Report" -EDefault "-TTestCase Y" ".......\XYZ\xyz.xml"

The disadvantage of this :- the report which is generated for 1st project (having tags X) is overwrite by the 2nd project(having tag Y). By which we will not get total count of both tests.