Yes, it is a complicated game with multiple nations. Israel has the right to secure it's borders from Iran, and Russia is right in protecting it's mission in Syria. Now one may understand, why the plan to remove Assad by supporting terrorists, like it was done in many other places to promote "democracy", is possible only, if the initiator of this orange and not so orange revolutions sits far beyond the oceans, and really doesn't care about the consequences of it's actions.
Let the Russians sells Syria the S300 missiles , Israel has expertise and knowledge to destroy them, they already have had training on how to counter them, then these missiles will be made obsolete once IDF have shown their superiority. What the Russians don't realise Israel reigns supreme in advanced technology. They are already several steps ahead of the Russians, Israel stays silent on all their technological advancement in weaponry. Whereas ex -soviet union nation glorifies in advance their latest weapons. When any nation mocks Israel, they will come against Israel's shield and protector. The apple of his eye.
By the time the S400 and S500 comes into service, Israel will have solutions for them as well. Shalom...amen and amen.