if(Trigger.isUpdate){
  //first collect all the Club__c from account. why to query all the ABC_and_Sale_Summary__c
  List<String> listOfClubs = new List<String>();

  //create a map of change in Down payment with club and Date
  Map<String,Decimal> mapOfChangeDownPayments  = new Map<String,Decimal>();
  
  for(Integer x=0;x<Trigger.new.size();x++){
        var newAccount = Trigger.new[x];
        var oldAccount - Trigger.old[x];
        
        listOfClubs.add(newAccount.Club__c);

        //calculate amount difference 
        Decimal amountDifference = newAccount.Down_Payment__c - oldAccount.Down_Payment__c;

        //key for map will be date+ club . for example '7mar-vancouver'
        String key = newAccount.club__c + '-' + newAccount.date__c;

        //there may be a chance that 2 or more accounts with same key and club are updated together
        if(!mapOfChangeDownPayments.containsKey(key)){
            mapOfChangeDownPayments.put(key,amountDifference);
        }else{
            mapOfChangeDownPayments.put(key,mapOfChangeDownPayments.get(key)+amountDifference);
        }

  }

  //now you have clubs, query all the Sale summary record which belongs to these clubs
  List<ABC_and_Sale_Summary__c> listOfABC = [select id,club__c,date__c,sale_Summary_Revenue__c,ABC_Down_payment__c
                                              from ABC_and_Sale_Summary__c where club__c IN : listOfClubs];


  //now loop through the sales summary records, check if the mapOfChangeDownPayments contains amount change for them , if yes, update it
  for(ABC_and_Sale_Summary__c summary : listOfABC){
    if(mapOfChangeDownPayments.containsKey(summary.club__c + '-' + summary.date__c)){
       summary.ABC_Down_payment__c  = mapOfChangeDownPayments.get(summary.club__c + '-' + summary.date__c);
    }
  }

  //you can update the list at last
  update listOfABC;
}