Pacifism has no easy way out in this conflict. Of course one could (reasonably) argue more weapons kill more people in the long run — however people tend to have other values than just pacifism. Would one accept a peace when it is an injustice in the way it is executed? If yes, at which level of injustice does this stop to be the case? Any peace for any price as fast as possible is an easy stance to take in theory, but one that does fails to deal with the underlying currents that lead to the war in the first place. Not to speak of the signal this could send ("If you are stronger than your neighbor country just invade it, you will definitly get something out of it and in the end people will accept everything if there is some kind of peace in the end").

Same goes for weapons. One could easily imagine a situation in which no weapons deliveries will stretch a conflict out and lead to far, far more civilian casualties than if the conflict quickly moves into an phase where negotiations are something all sides of an conflict actually want. So a dogmatic "no weapons" stance can easily cost more lives than a more balanced stance that looks at things in a more nuanced way.

Ethically it depends. Are one's ethics about the strict enforcement of fundamental rules regardless of the outcome? Or are one's ethics about minimizing the harm that is created regardless of the rules that have to be broken to get there?

In reality everybody will fall somewhere between those poles.