ESOUI - Blocking Chat messages

Hello, I'm writing a simple Addon that block Zone Message everywhere except Cyrodiil/Craglorn. The test chat message display I've inserted in the Addon works correctly, the only thing missing is I can't find a way to block chat message from displaying. I've checked the wiki for events/functions but I can't find a way to block them. How should I block chat messages from displaying ?

Here is the code I've written so far.

Lua Code:

ZonePug = {}
ZonePug.name = "ZonePug"
 
function ZonePug.OnInitialized(eventCode, addOnName)
    if (ZonePug.name ~= addOnName) then return end
    EVENT_MANAGER:RegisterForEvent(ZonePug.name, EVENT_CHAT_MESSAGE_CHANNEL, ZonePug.OnChatMessage)
end
 
function ZonePug.OnChatMessage(eventCode, messageType, fromName, text, isFromCustomerService)
    if messageType == CHAT_CHANNEL_ZONE then
        if GetCurrentMapZoneIndex() == 499 or GetCurrentMapZoneIndex() == 37 then
            df("%s has detected a zone message in Craglorn/Cyrodiil, let it display", ZonePug.name)
        else
            df("%s has detected a zone message elsewhere, block it", ZonePug.name)
            -- Insert block code
        end
    else 
        df("%s has detected a non zone message, do nothing", ZonePug.name)
    end
end
 
EVENT_MANAGER:RegisterForEvent(ZonePug.name, EVENT_ADD_ON_LOADED, ZonePug.OnInitialized)

function MyOnChatEvent(control, ...)
    --Setting enabled?
    secondsSinceMidnight = 0
    if settings.enableChatBlacklist and settings.chatKeyWords ~= nil and settings.chatKeyWords ~= "" then
        if settings.blacklistedTextToChat then
            --Get the current time
            secondsSinceMidnight = GetSecondsSinceMidnight()
        end
        --Filter the incoming chat message now
        local chatMessageWasBlacklisted = MyFunctionToCheckIfMessageWasBlacklistedWithBooleanReturnCode or false
        if chatMessageWasBlacklisted then
            --Abort the chat event function so no text is shown in the chat
            return true
        end
    end
    --Call the original chat event method now to show the text in the chat
    return false
end
ZO_PreHook(CHAT_SYSTEM, "OnChatEvent", MyOnChatEvent)

ZonePug = {}
ZonePug.name = "ZonePug"
 
function ZonePug.OnInitialized(eventCode, addOnName)
    if (ZonePug.name ~= addOnName) then return end
    ZO_PreHook(CHAT_SYSTEM, "OnChatEvent", ZonePug.OnChatMessage)
end
 
function ZonePug.OnChatMessage(eventCode, messageType, fromName, text, isFromCustomerService)
    if fromName == CHAT_CHANNEL_ZONE then
        if GetCurrentMapZoneIndex() == 499 or GetCurrentMapZoneIndex() == 37 then
            -- df("%s has detected a zone message in Craglorn/Cyrodiil, let it display", ZonePug.name)
        else
            -- df("%s has detected a zone message elsewhere, block it", ZonePug.name)
            return true
        end
    else 
        -- df("%s has detected a non zone message, do nothing", ZonePug.name)
    end
end
 
EVENT_MANAGER:RegisterForEvent(ZonePug.name, EVENT_ADD_ON_LOADED, ZonePug.OnInitialized)