current zlibwapi.dll in place is IPP one.
the tool has two commands, in both it makes use of zlib compression function. To see timings, I have used timer program here.

The first command "e" makes use of both zlib compress and zlib decompress, first it inflates the zlib stream found inside sample file then it compresses that in-memory as well.
while the second "d" command makes use of zlib compress only so in both cases IPP ZLib should have helped.


Execute these commands on cmd :-

timer.exe ZTool e:pzlib:m2:x:r9:t1:cm0 sample sample.out
and then this :-
timer.exe ZTool d:pzlib:t1:cm0 sample.out sample.orig

Dont think that "d" means decompress here, it makes use of zlib compression so IPP should help here, at least thats what we thought.

Once one we checked timings for IPP, we rename zlibwapi-default.dll to zlibwapi.dll to use with the program ZTool.
Now we repeat same steps :-
timer.exe ZTool e:pzlib:m2:x:r9:t1:cm0 sample sample.out2
timer.exe ZTool d:pzlib:t1:cm0 sample.out sample.orig
and count the timings then compare them with IPP's.

Both "e" and "d" commands makes use of zlib compression and in both IPP ZLib was slower than normal one.