Easiest thing would be the use of a key, like google maps, where you can select/filter Pins from the Key if the Pin on the map is inaccessible.
With regards to zooming, if you are in a situation where there are too many pins wouldn’t it be better to break the map into regions and have a pin/region if there is anyone in that area. Once you have zoomed into that area you can replace it with the correct pins.