The Short Version
Multiple peer-reviewed studies directly confirm that zinc oxide is the end product of thermally decomposing zinc nitrate hexahydrate, fully supporting the claim's assertion that ZnO "can be synthesized" this way. The process does involve intermediate stages (dehydration, basic nitrate formation) before ZnO is obtained, and conditions such as temperature and atmosphere affect the outcome, but these details do not contradict the claim. The modal phrasing ("can be") requires only that the synthesis is feasible, which the evidence clearly establishes.