IMO, China keeping zero-covid strategy at this point is just flexing.
They are just being extra careful because they can.
Even if China opens up more, they have a strong contact tracing system that would be able to cut down infections within weeks.
Case counts and deaths are declining even in the US.
If a country has good vaccination levels (80+%), then basically there is not much to be afraid of. Death rate of below 1 per 100,000 means it is much safer than getting into a car.
China has the luxury can wait and see how the other countries are coping with opening up, the longer term efficacy of vaccines (both western and Chinese), and whatever other data they wish to observe. Something like how in certain areas of US and Canada uneven vaccination rates caused localized spikes in hospitalizations.
Once they have the whole spectrum of available vaccine technologies, I would imagine they will start opening travel bubbles with other low case countries with good relations like NZ or UAE.
The next step will also be vaccinating Africa.
China has a big role to play, all the top vaccinated countries in that list use Chinese vaccines. Higher roll outs to the continent will move Belt and Road projects further forward, and allow more business to normalize.