[XanDDemoX]

I had a similar problem, needing to resolve zoneIndex within a city map within my addon.

I managed to get round it using a combination of a lookup, GetMapTileTexture and GetCurrentMapZoneIndex.

These two functions handle strings. Pattern matching from GetMapTileTexture and string keys used in the lookup.

local function GetMapZone(path)
    path = path or GetMapTileTexture()
    path = string.lower(path)
    local zone,subzone = string.match(path,"^.-/.-/(.-)/(.-)_")
    if zone == nil and subzone == nil then 
        -- splits if path is actually a zone key 
        zone,subzone = string.match(path,"^(.-)/(.-)$")
    end
    return zone,subzone
end
 
local function GetMapZoneKey(zone,subzone)
    if zone == nil and subzone == nil then 
        zone,subzone = GetMapZone()
    elseif subzone == nil then
        zone,subzone = GetMapZone(zone)
    end
    return table.concat({zone,"/",subzone}),zone,subzone
end

This function creates a lookup where you can lookup zone by zoneIndex, "zone/subzone" or "zone" or "subzone".

local function CreateLocationsLookup(locations,func)
    local lookup = {}
    func = func or function(l) return l end 
    local item
    for i,loc in ipairs(locations) do 
        item = func(loc)
        
        lookup[loc.zoneIndex] = item
        lookup[loc.key] = item
 
        if lookup[loc.subzone] == nil then 
            lookup[loc.subzone] = item
        elseif lookup[loc.zone] == nil then 
            lookup[loc.zone] = item
        end
        
    end
    
    for i,loc in ipairs(locations) do 
        if lookup[loc.zone] == nil then 
            lookup[loc.zone] = lookup[loc.zoneIndex]
        end
    end
    
    return lookup
end

Example location table for CreateLocationsLookup

local _locationsList = {
    [1] = 
    {
        ["zoneIndex"] = -2147483648,
        ["mapIndex"] = 1,
        ["tile"] = "art/maps/tamriel/tamriel_0.dds",
    },
    [2] = 
    {
        ["zoneIndex"] = 2,
        ["mapIndex"] = 2,
        ["tile"] = "art/maps/glenumbra/glenumbra_base_0.dds",
    },
}

Function to resolve zones from lookup

local function GetZoneLocation(lookup,zone,subzone)
    local loc
    
    if type(zone) == "number" then 
        loc = lookup[zone]
        zone = nil 
    end 
    if loc == nil then
        local key,zone,subzone = GetMapZoneKey(zone,subzone)
        
        -- try by zone/subzone key first
        loc = lookup[key]
        -- subzone next to handle places like khenarthis roost
        if loc == nil then
            loc = lookup[subzone]
        end
        -- then zone to handle locations within main zones which cannot be matched by key e.g coldharbor's hollow city
        if loc == nil then 
            loc = lookup[zone]
        end 
    end 
 
    -- if zone cant be found then return tamriel
    if loc == nil then 
        loc = lookup["tamriel"]
    end
    
    return loc
end

Usage example.

local list = {} -- table of zones like example table.
 
local lookup = CreateLocationsLookup(list)
 
local loc = GetZoneLocation(lookup,GetCurrentMapZoneIndex())

Something that also got me was the map on player activate. It appears to change from the Tamriel map.

I handled it like below:

addEvent(EVENT_PLAYER_ACTIVATED,function(eventCode)
                
        local func = function()
                        local loc = GetZoneLocation(lookup,GetCurrentMapZoneIndex())
        end 
        
        local idx = GetCurrentMapIndex()
        
        -- handle the map changing from Tamriel 
        if idx == nil or idx == 1 then 
            local onChange
            onChange = function()
                func()
                removeCallback(CALLBACK_ID_ON_WORLDMAP_CHANGED,onChange)
            end 
            addCallback(CALLBACK_ID_ON_WORLDMAP_CHANGED,onChange)
        else
            func()
        end 
 
    end)

Hope all of that makes sense You can also see it in LocationData.lua, and usage in FasterTravel.lua in the addon.