Presents phospholipase and nuclease activities, depending on the different physiological conditions. Plays a key role in mitochondrial fusion and fission via its phospholipase activity. In its phospholipase role, it uses the mitochondrial lipid cardiolipin as substrate to generate phosphatidate (PA or 1,2-diacyl-sn-glycero-3-phosphate), a second messenger signaling lipid. Production of PA facilitates Mitofusin-mediated fusion, whereas the cleavage of PA by the Lipin family of phosphatases produces diacylgycerol (DAG) which promotes mitochondrial fission. Regulates mitochondrial shape through facilitating mitochondrial fusion. During spermatogenesis, plays a critical role in PIWI-interacting RNA (piRNA) biogenesis (By similarity). piRNAs provide essential protection against the activity of mobile genetic elements. piRNA-mediated transposon silencing is thus critical for maintaining genome stability, in particular in germline cells when transposons are mobilized as a consequence of wide-spread genomic demethylation. Has been shown to be a backbone-non-specific, single strand-specific nuclease, cleaving either RNA or DNA substrates with similar affinity (By similarity). Produces 5' phosphate and 3' hydroxyl termini, suggesting it could directly participate in the processing of primary piRNA transcripts (By similarity). Has been proposed to act as a cardiolipin hydrolase to generate phosphatidic acid at mitochondrial surface. Although it cannot be excluded that it can act as a phospholipase in some circumstances, this activity could not be confirmed (By similarity). a cardiolipin + H2O = 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) + a 1,2-diacyl-sn-glycero-3-phosphate + H(+) Homodimer. In contrast to other members of the phospholipase D family, contains only one PLD phosphodiesterase domain, suggesting that it has a single half-catalytic and requires homodimerization to form a complete active site. Belongs to the phospholipase D family. MitoPLD/Zucchini subfamily.