Braun has 'Negotiating with the Coalition' which you can use twice, the 'Inter-Party Relationships' card, any option which condemns the KPD on 'Choosing Our Enemies', banning the KPD paramilitary/ further persecuting them, reducing welfare spending, and siding with employers in labour disputes.
This all got me to very friendly with Z & DVP.
Not sure what difference this makes in practice tbh.