Its very simple and should be clear:
INPUT: P3=IF(AND(H23=EFH/ZFH,H35=Ja),L21,IF(AND(H23=REH,H35=Ja),L22,IF(AND(H23=RMH,H35=Ja),L23,0)))
OUTPUT:
=IF(H23=EFH/ZFH && H33=Ja;P3=L21;IF(H23=REH && H33=Ja;P3=L22;IF(H23=RMH && H33=Ja;P3=L23;P3=0)))
Of course it should also work with more sub IF's
I can give a basic script that already makes part of conversion...