It is not enough to say that it is Zelkova. It is necessary to find out which Zelkova this is: Caucasian (Carpinifolia), Japanese (Serrata), Chinese (Schneideriana/Sinica)...? It could be any of these three, although it most resembles the Japanese Zelkova, which is not 100% reliable. In any case, it is neither Cretan nor Sicilian Zelkova. It is also unlikely that it is a Chinese Zelkova, so it is either Japanese or Caucasian. In Europe, Caucasian is much more common, while in the USA, Japanese predominates, as far as I know.
The easiest way to reliably determine it is to find a mature tree nearby and compare the leaves, bark... With such young saplings, the determination is not the most reliable.