I did some reading while at home. My primary source was: H. Remy, Lehrbuch der anorganischen Chemie (oldy but goldy),
Cotton Wilkinson, Advanced inorganic chemistry and
Jander, Hofmann, Qualitative Analyse.
According to Remy , Zr should dissolve easily in aqua regia.
I suppose that reducing the solution repeatedly to dryness adding fresh HNO3 should do the trick to get ZrO (NO3)2 x nH2O.
Alternatively, Zr Remy states that Zr dissolves in molten NaOH under formation of Hydrogen.
You can dissolve the cold melt in diluted HNO3. This has the advantage that no chloride is present.
If you hydrolize some solution and thus deposit fresh ZrO2 (with much hydroxide still), it will readily dissolve in acids before it ages.
Alternatively,