# [Haskell], 84 bytes

<!-- language-all: lang-hs -->

    import Data.List
    z=zipWith
    f l=foldr1(z$z(+))$scanr(\_->transpose.map reverse)l"abc"

[Try it online!][TIO-jcng0izt]

[Haskell]: https://www.haskell.org/
[TIO-jcng0izt]: https://tio.run/##bVBNU4MwED2bX7EyPbQjdgikrRzw4Hhrxx50xgMyFtsgjHwNSbXlz1dIsAnUHHbgvbdv324csi@apqdTkpVFxeEx5OF0lTCOaq9OyteExyiC1IuKdFfhcT2qxzeTyYhtw7wav73f3vMqzFlZMDrNwhIq@k0rRiepEX5sjdNhw@Jin@4e6OYIHpR7/syrVQ4Z@0RXPzGtaPvZMEkEB887Ao9pDsZ6OTWApoyC8bR@gfXy2kAoC5O8Ue4KQNC8CHwfBwGoCQ1AggAp1gQnMMVv83zbBDLUYwtMAGxpsjOkO5EWg7moC8GTc4svYGyL6sg6IEGQ4AyG@TMBY63fvthIaBwx1BYxyEwZSMSxtLpQrOzSWVuLLZ07h0XnfLm0jD6T0SWirtWc605grtpB7gOurnI0QlrhwRVbK6GyLe3Kna2u6s1QhjAfXk5uZguNI/QED27QXkEyusqVfb38WPEy4B/Si@b@70X6KqKydI5ulytAp18 "Haskell – Try It Online"