The issue is not whether or not Iran economy will be broken, the issue here is who can hold on longer, economy does not break down overnight, it takes some time to do it, and you also have buffered economy, look at Russia for example, if we applies Russian economy policy in the US, our government would collapse in probably no more than 12 months, yet they held on for 5 years between 12 to 14.5% national interest rate, mostly because Russia had an Iron grip on their people and they have ways to bypass Sanction.
Iran won't have that, but it still doesn't mean they will collapse overnight. Any economic impact on Iran will be felt in the mid- to long term, which means you have to wait a few months before it starts hitting the streets. Do we have a few months to wait? Bear in mind, Summer is around the corner, and we have a mid-term in 6 months plus change.
And that is if we assume China won't bankroll Iran's war like the EU bankrolling Ukraine. At this moment, China is doing nothing, but it can change, and most likely will change in the mid-course.