Putin is very much asking for it, but Zelensky or elements within Russia should pull the trigger.
Moscow itself or or any other Russian city would be collateral damage much less than what Russia has inflicted since February.
Putin seems to be rapidly ramping up both the threat and execution of his escalation. Napalm, cluster, and phosphorus munitions are being fired by Russians in the Donbas. The threats grow more shrill and ominous.
This would necessitate following up with hitting anything military that moves within Russia till what is left all holds still. The gamble is that what remains in and emerges from the rubble will be less bold and less crazy than the crazy Putin has reached and is headed toward.
If the rat is really feeling this cornered, it might be time to think about fragging it, or at least updating that set of contingency plans.