Mac 10.10 & 10.11 can not open IDL 8.1

Use ln in terminal.

relinked the file libz.1.dylib (which on my system is located in: /Applications/exelis/idl82/bin/bin.darwin.x86_64), which in fact is linked to this file in the same folder libz.1.2.3.dylib,  to the file libz.1.dylib in /user/lib/

ln -s /usr/lib/libz.1.dylib libz.1.dylib