technically.. you COULD.. however i would not reccomend it. many times the hyds sump leaks and mingles with the rear axle sump due to the seal that the pto shaft passes thru wearing and not getting replaced.. ever...
that means 'jack oil' will be diluting your rear end oil.
I'd use UTF in both sumps.. or gear oil in the rear end, and utf in the hyds.
at least if utf mingles with the gear oil.. it is still a gear-safe lubricant.. unlike plain hyd oil..