To initialize your local repository using the GeeksPhone Zero trees, use a command like this
repo init --repo-url=git://git.omapzoom.org/tools/repo.git -u git://github.com/gpzeroDev/android.git -b gingerbread

repo sync

To compile GP0 SR ROM you only need to do this:
vendor/geeksphone/zero/tools/build.sh

If you do this steps, you will have an update.zip and update-fastboot.zip files with the ROM!