Handling Deposits to Vendors and how to book this

Handling Deposits to Vendors and how to book this

Our scenario:

1. We rent equipment from a renting company for a project (Vendor "Eurorent")
2. We receive an order confirmation with a request to pay a deposit of € 1500. (this is not a Bill)
3. We pay a deposit of € 1500 for the equipment.
4. After using the equipment for x amount of time we return it.
5. Now Eurorent calculates the total cost for the rent which is € 1000.
6. They deduct the €1000 from the deposit we've payed.
7. So instead of paying, we will get € 500 in return.
8. We receive an invoice for € 1000 from Eurorent. The invoice is marked as payed.

The question is: how should we handle this correctly in Zbooks?

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For step 3. I believe we should book the deposit of € 1500 as a Payment made "somewhere".
For step 8. we should book the Bill of € 1000 and record the payment with payment date on the date we payed the deposit amount?
... I'm lost already..

This is a non-conventional scenario but here in Belgium we encounter this all the time.
Educating all vendors to suit our system is not an option.

Please advice.