I am considering using a 770 (or its replacement) for both 990 zones. Zone 1 will be 5 4-Ohm speaks while zone 2 is a pair of 8-Ohm speaks. Is there any problem for the either amp in pushing these mixed Ohm loads?

Nope.

no way to know for sure, until the new amp is released....

There should be no problem with either the 770 or a replacement 200Wx7 amp driving such a mix of loads.

Thanks for the replies. I am now just impatiently waiting for the new amp to come out. I do like the new look much better.