1. Question: Rav Elchanan Wasserman (Kovetz Ha’aros 77, 78) asked why you are punished for each child when shechting a cow with its calves but you are only punished once for wearing a piece of wool clothing with shaatnez that has multiple linen threads intertwined in it?
A. Even though there is an argument between the Rabbanan and Sumchus (See Chullin 82a) whether the shochet gets one set of lashes or multiple sets for each calf just as Sumchus would say if you eat two forbidden fats in one setting you are liable for two sets of lashes but the Rabbanan still hold according to the Rambam in his commentary on Mishnayos Nazir (Chapter Shlosha Minim) that though you might only get one set of lashes but you still are liable in heaven for each calf. Why is this if what triggers the sin is really just one action of slaughtering the mother?
B. Same should apply to wearing shaatnez clothes, even though it is one action of wearing but if there are multiple threads of interwoven wool and linen you should at least be liable in heaven for each thread?
Answer: By the slaughtering there is really two different issues here shechting the mother and her first child and then her second child the sin was just done in one action once the mother was slaughtered so it’s doing two prohibitions at once. But by shaatnez the prohibition is wearing clothing that has shaatnez in it so really there is only one prohibition and multiple reason of why he is liable. But he is only punished once for the one prohibition.