Or you could simply put in as many single heatpumps....no zones. The advantage being a much higher COP (for heating) and SEER rating ( for cooling) and add TUYA remote control units ( think of them as IOT control remotes in your hand) . They cost about a tenner each .... When programmed.... They can act like one whole unit or separates. Much cheaper and more efficient. These units can be bought for about 1000 each, install is about 750. COP and SEER around 4-5 for each of the units.
Have yet to see a multi zone unit with a high COP or SEER rating.
The added advantage is that if one breaks ... The rest are still functioning 👍
then you have to have the same number of outdoor units outside taking up space and creating more noise. there is more to it that what you have pointed out.