Currently I have a 3 port valve controlled by a Time Controller
(Honeywell ST799), which controls my heating and hot water.

I want to zone my house to split upstairs and downstairs, and would
therefore like to use two sets of the HoneyWell CM67RF Programmable
Thermostat and HC60NG relay box, one set for each zone. What I would
like to know is what kind of zone valves I need?

I could buy three 2 port valvles (1 for upstairs zone, 1 for downstairs
zone, and 1 for the Hot Water (HW)). However at =A345 a valve I would
like to know if it is possible to re-use the existing 3 port zone valve
for one of the zones and HW, (in which case the CM67RF + HC60NG and the
ST799 would need to be able to ontrol the same valve, is this possible?