I Don't think "xZlib" is the problem,I did many tests!
The parameters of "ue4dt" are the problem !
when i use ue4dt with default mode (without any parameters)
the game installs without any problem(no longer slowly installation) ! but the ratio of compression is less good (48.1gb ---------->34gb)!
with these parameters:
"UE4DT.exe" e -m1 -c1024m -b1024
i got , like i told previously a good compression ratio (48.1gb ---------->24.7gb) but a very very very long & slow installation!
maybe a better configuration of parameters could solve this !
thx !