1) Install 7z using zypper
(first use zypper search to find the name, then zypper install)

2)Then uze "7z x" to extract flex-2.6.0  (see the manual using man 7z)

3) Try to install lexical analyzer manually, 
using ./configure, make, make check (or make tests or make all), make install, make clean or make distclean.

Note 1: The source files of flex are in https://sourceforge.net/projects/flex under files (you may obtain them also using wget command)
        If sources are in github, you can use: git clone https://.../file.git
Note 2: The binaries of the package may exist in your distribution, e.g., check using zypper search flex in OpenSuse Leap 16

(The process is the same for bison and many other packages)
