Is it permissible to wash a garment stained with maniyy (seminal fluid) and madhiy (pre-seminal fluid) along with another clean garment in the same basin with water and soap, knowing that they will both be rinsed together at the end? And does this lead to the clean garment becoming impure?

Semen is pure, and it is permissible to wash a garment stained with semen along with other garments. As for madhy (pre-seminal fluid), it is impure by consensus, and it is not permissible to wash it along with other garments in a single vessel containing less than two qullas of water if the clothes are placed on the water, unless the water is poured over the impure garments.