MC Access: Create Select query that always returns value

Good day! I hope someone can help me. Below I wrote down my structure and question. I have this invoice details table: Invoice Details Table

 Invoice | Detail | Product | Price | VAT % | VAT € | TOTAL |
 ------- | -------|---------|-------|-------|-------|-------|
 0001    |   1    |     X   | € 100 |  21   | € 21  | € 121 |
 0001    |   2    |     X   | € 200 |  21   | € 42  | € 242 |
 0001    |   3    |     X   | € 100 |   6   | €  6  | € 106 |

Now I want to make a select query to get the following values:

Desired query result:

 Invoice | SumofVAT 6% | SumofVAT 21% | 
 ------- | ------------|--------------|
 0001    |   €6        |     € 63     | 

After this query I can use an update query to write this Data to my invoice table:

 Invoice | Client | Date    | Price | VAT 6% | VAT 21% |
 ------- | -------|---------|-------|--------|---------|
 0001    |   B10  |01-01-01 | € 469 |  € 6   | € 63    |

I have tried many things. The problem I run into is that when a particular only has one or more products with 1 type of VAT in %. Then the query returns Null.

I think I should have:

1) a query to calculate total VAT 6% in € for invoice xxxx ( return invoice number and total vat of 6%)

2) a query to calculate total VAT 21% in € for invoice xxxx ( return invoice number and total vat of 21%)

3) If one of these queries returns Null it should return invoice number and total number of VAT € 0,00

Hope someone can help me with this.