The big question is what will Russia do? Maybe launch a full scale offensive into the Ukraine? We will be faced with a two front war then. Iran might join in as well and invade Saudi Arabia via Iraq which will probably be their ally. Yes, this situation will go nuclear quickly.
Ukraine? Well, its been a lost cause for a while now, unfortunately.
Saudi Arabia? That’s not as easy. The Saudis have a well-equipped military and has strong alliances with the rest of the GCC militaries as well as the U.K., France, Egypt, Turkey and Pakistan (I’m not even mentioning the U.S. here). Other than non-conventional weapons, Iran is at a disadvantage in every sense.