Pakistan and Iran can unite on only one ground and that is against the US. Other than that our enemies are not the same. Iran considers India a friend while we are bitter rivals. Iran considers Saudi Arabia an enemy, we on the other hand consider them as friends. So only common enemy remains is the US and many Pakistani elites would rather die first than to go against the US as much of their own property and children resides in US and UK. So a no on that as well unless some nationalist wins over.
I personally want some sort of alliance between regional countries such as Iran, Pakistan China and Russia against this Bully.