Daniela,
Analyzing the Tab Conditions, in the sales order; probably the exclusion functionality could be activated.
In other words from the discounts only one discount is getting a value (ZC01).
Could you please test with giving a discount value to ZR01 that is more than value given for ZC01?
Another way of checking is see if any exclusion group is assigned to your pricing procedure.
Path
IMG>SD>Basic Functions>Pricing>Condition Exclusion>Condition Exclusion for Groups Of Conditions
Maintain Condition exclusion for pricing procedure
Exclusion -
Check if in V/06, for condition type ZC01, field Exclusion is activated.
And check in V/08, the pricing procedure, for other discount condition types, the requirement is 2.