We have version 0.86 of ICSharpCode.SharpZipLib.dll and it is not .NET Core compatible.
There appears to be two main (and several more) "latest" version of it. SharpZipLib and SharpZipLib.NETStandard, both by ICSharpCode.
Which is the correct one to use for .NET Core?
SharpZipLib runs on .NET Standard 2.0 in 2018.
Changes
The targeted frameworks are now:
.NET Standard 2.0 netstandard2 (Core 2.0+, FW 4.6.1+, Mono 5.2+, UWP 16299)
.NET Framework 4.5 net45 (Mono 4, Dependency-free on Windows 8+/2012+)
See: https://github.com/icsharpcode/SharpZipLib/wiki/Release-1.0
Use this one: https://www.nuget.org/packages/SharpZipLib/