Sony is cooking up an Xperia 2 smartphone and it will take the role of a something akin to its Compact line of models in the past. It will offer many of the flagship Xperia 1 features but will come in a less tall 6.1-inch display and smaller overall dimensions accordingly.
https://www.notebookcheck.net/First-Sony-Xperia-2-details-leak-out-looks-to-be-a-compact-Xperia-1.420647.0.html
158mm is not really compact. It is the size that was average 3 years ago. The xz1 compact it 130mm.