It is not possible to connect two pairs of speakers with different impedances to the CXA61/81/81MKII.
When using two pairs of speakers then it is important that both sets have a nominal impedance rating of 8 Ohms, and this is to ensure that the overall impedance does not dip below 4 Ohms. If the overall impedance drops below 4 Ohms then this will cause the amplifier to run hot and could cause damage.