vertical tabs have been a life changer, but you don't need zen for that anymore, firefox has it natively (thank allah). but i also use a 1440p monitor so im perfectly fine with losing a little screen real estate, but that + removing the bookmarks bar makes it look so slick and imho is way more intuitive since the horizontal tabs eventually clump up and you lose track of what tab is what whereas the vertical one is always clear but you can also indent groupings. highly recommend giving it an honest shot but obv you do you