Please note Zephir is currently in Alpha stage and therefore bugs can be expected.
You need to have certain packages installed:
In the command line type:
sudo apt-get install libjson0 libjson0-dev libjson0-dbg
sudo apt-get install re2c
Once you have the required packages installed, you can generate the parser as follows:
./generate
Compile the extension (this is your code):
./zephir
The code produced is placed in ext/, there you can perform the standard compilation:
cd ext/
sudo ./install