I lived in Shenzhen for a few years and I figure the only way you could survive the zombie apocalypse in a city like that would be to barricade the stairwells and elevators and then push stuff up one stairwell at a time. You'd could live off the food in the apartments as you went up. The goal would be to live on the roof of the complex and create enough compost to start a garden on the roof of the skyrise.
There would be no hope of escape to the lower levels as it would be flooded with a zombie population of over 10 million. You and your children would have to work your way through it over the years until the ghost of the city became a habitable zone again.