Catalyzes the reversible cleavage of L-rhamnulose-1-phosphate to dihydroxyacetone phosphate (DHAP) and L-lactaldehyde (PubMed:12962479). Also catalyzes the dephosphorylation of phospho-serine in vitro (PubMed:25848029). L-rhamnulose 1-phosphate = (S)-lactaldehyde + dihydroxyacetone phosphate Binds 1 zinc ion per subunit. Carbohydrate degradation; L-rhamnose degradation; glycerone phosphate from L-rhamnose: step 3/3. Homotetramer. Induced by L-rhamnose via the RhaR-RhaS regulatory cascade. Binding of the cAMP receptor protein (CRP) is required for full expression. Belongs to the aldolase class II family. RhaD subfamily.