It's just 1% slower then regular zlib, but in pure nim. This is a big deal. Does not require zlib1.dll or C. zlib had like 20 years of effort put into optimizing it, with nim you were able to achieve nearly same perf nim much shorter time.
You have solving the HTTP gzip'ed payload problem. This lib should be installed by default as part of nim install. I have run into zlib1.dll not matching windows 32/64 bit before. Its really annoying. This is really cool. Its obvious what I will be using from now on.