Catalyzes the decarboxylation of 3-oxo-tetronate 4-phosphate to dihydroxyacetone phosphate (DHAP) and CO(2). 3-dehydro-4-O-phospho-D-erythronate + H(+) = CO2 + dihydroxyacetone phosphate 3-dehydro-4-O-phospho-L-erythronate + H(+) = CO2 + dihydroxyacetone phosphate Binds 1 zinc ion per subunit. Deletion mutant is unable to use L-threonate or D-erythronate as a carbon source. Belongs to the aldolase class II family. AraD/FucA subfamily.