Re: PIC32MZ EF Secondary Oscillator
... which would require you to disable soscen and tristate the oscillator amp that would fight your external oscillator. I am sure that is what the datasheet intends.
Alternately, you can feed sosci via a large resistor (assuming that the amp works at all - given the errata), enable the oscillator and let it drive the buffer. At 32KHz there is little, if any, power differential.