Zen (and Arc) are much more than just vertical tabs. Native, neatly integrated support for vertical tabs is amazing and a step in the right direction but it's far from Arc in terms of usability, the main missing thing being the lack of "spaces" (ie. in the vertical sidebar you can swipe left/right to get a different space of tabs with different bookmarks)
leawi · · focus · HN ↗
thiht · · focus · HN ↗