Hi, I've built a trigger that will update the Owner for the Account and its related contacts based on the User Lookup field in the Account. I was able to update the Owner of related contacts with an update in the Account.
If I change the Account in any of the Contact then the new Accounts owner should be added as Contacts Owner. I tried using the Trigger.OldMap. Can someone help me with what needs to be changed in my trigger...

trigger AccountOwnerUpdate on Account (before insert, before update) {
    Set<Id> accIds = new Set<Id>();
    List<Contact> updatedConList = new List<Contact>();
    Map<Id, String> newOwnerIds = new Map<Id, String>();
    
    
    List<Contact> conList = [SELECT Id, AccountId FROM Contact WHERE AccountId IN: accIds];
    for(Account acc : trigger.new) {
        accIds.add(acc.Id);
        newOwnerIds.put(acc.Id, acc.Coverage_Lead__c);
        
        if(acc.Coverage_Lead__c != NULL) {
            acc.OwnerId = acc.Coverage_Lead__c;
        }
        if(acc.Coverage_Lead__c == NULL){
            acc.OwnerId = acc.LastModifiedById;                
        }
    }
    if(trigger.isUpdate) {
        for(Account acc : trigger.new) {
            for(Contact con : conList) {
                if(con.AccountId!= NULL) {
                    if(trigger.oldMap.get(con.Id).AccountId != con.AccountId) {
                        accIds.add(con.AccountId);
                    }
                }
                accIds.add(trigger.oldMap.get(con.Id).AccountId);
            }
        }
    }

    for(Account accs : [SELECT Id, LastModifiedById, (SELECT Id, Owner.Id, AccountId FROM Contacts) FROM Account WHERE Id IN:accIds]) {
        if(newOwnerIds.get(accs.Id) != NULL) {
            for(Contact con : accs.Contacts) {
                con.OwnerId = newOwnerIds.get(accs.Id);
                updatedConList.add(con);
            }
        }
        if(newOwnerIds.get(accs.Id) == NULL) {
            for(Contact con : accs.Contacts) {
                con.OwnerId = accs.LastModifiedById;
                updatedConList.add(con);
            }   
        }
        
    }
    update updatedConList;
}

Thanks in Advance.