foreach (var itemCount in itemCounts)
{
    var addItemTracking = new ItemTracking
    {
        availabilityStatusID = availabilityStatusId,
        itemBatchId = itemCount.ItemBatchId,
        locationID = locationId,
        serialNumber = serialNumber,
        trackingQuantityOnHand = itemCount.CycleQuantity
    };
    _context.ItemTrackings.Add(addItemTracking);
    _context.SaveChanges();
    var addInventoryTransaction = new InventoryTransaction
    {
        activityHistoryID = newInventoryTransaction.activityHistoryID,
        itemTrackingID = addItemTracking.ItemTrackingID,
        personID = newInventoryTransaction.personID,
        usageTransactionTypeId = newInventoryTransaction.usageTransactionTypeId,
        transactionDate = newInventoryTransaction.transactionDate,
        usageQuantity = usageMultiplier * itemCount.CycleQuantity
    };
    _context.InventoryTransactions.Add(addInventoryTransaction);
    _context.SaveChanges();
}

var addItemTracking = new ItemTracking
{
    ...
}
_context.ItemTrackings.Add(addItemTracking);
var addInventoryTransaction = new InventoryTransaction
{
    itemTracking = addItemTracking,
    ...
};
_context.InventoryTransactions.Add(addInventoryTransaction);
...
_context.SaveChanges();

itemTrackingID = addItemTracking.ItemTrackingID,

addItemTracking.InventoryTransaction = addInventoryTransaction;

var trackingItems = itemCounts
    .Select(i => new ItemTracking
        {
            availabilityStatusID = availabilityStatusId,
            itemBatchId = i.ItemBatchId,
            locationID = locationId,
            serialNumber = serialNumber,
            trackingQuantityOnHand = i.CycleQuantity
        });
_context.ItemTrackings.AddRange(trackingItems);
_context.SaveChanges();

var inventoryTransactions = trackingItems
    .Select(t => new InventoryTransaction
        {
            activityHistoryID = newInventoryTransaction.activityHistoryID,
            itemTrackingID = t.ItemTrackingID,
            personID = newInventoryTransaction.personID,
            usageTransactionTypeId = newInventoryTransaction.usageTransactionTypeId,
            transactionDate = newInventoryTransaction.transactionDate,
            usageQuantity = usageMultiplier * t.trackingQuantityOnHand
        });
_context.InventoryTransactions.AddRange(inventoryTransactions);
_context.SaveChanges();