Last week’s helpmate solves like this (don’t forget that Black’s moves are recorded first in helpmate solutions):

1. Kb3 Bd2 2. c1N Kb1 3. Ka3 Kc2 4. Ka2 Bxb4 5. Ka1 Ba3 6. Na2 Bb2#

The second part, with the bishop on c1 replaced by a white knight

1. b3 Ne2 2. c1R+ Kb2 3. Ra1 Kc3 4. Ka3 Kc4 5. Ka2 Kb4 6. b2 Nc3#