Zurich is one of the gentler European cities for anyone bringing parents or pushing a stroller, but it is not uniformly easy. Transit is the strong part: the Cobra and Flexity cars that make up most of the VBZ tram fleet are low-floor, city buses are low-floor and kneel at the kerb, and both Zürich HB and the airport station are lift-served. It is not yet uniform, though. Older high-floor trams still turn up on some lines, and VBZ publishes accessibility line by line rather than promising it everywhere — so if you are in a chair, check your specific line on the VBZ site before you set out, and let an awkward tram go rather than fighting a step.
The Old Town is the hard part, and it is hard in a specific way. Kreis 1 is cobbled, and the lanes climbing to Lindenhof and up to St. Peter are steep enough that a wheelchair needs a second pair of hands and a heavy stroller is a workout. It is short, though — this is not Lisbon or Porto, where the hills go on for kilometres. Flat, easy alternatives are close by: the Seefeld and Enge lake promenades are level and pram-friendly for as long as you want to walk, the ZSG boats board from the quay, and Uetliberg is reached by S-Bahn rather than on foot, though the final stretch from station to lookout is uphill on gravel.
Two practical things that catch GTA families. Sunday is a genuinely closed day — shops shut, with station retail the standard exception — and most museums, the Kunsthaus included, close on Mondays; land on the wrong pair of days and a short trip loses a lot. And summer is usually kinder than a Toronto July, with public drinking fountains everywhere for refills — though Zurich does get proper heatwaves, and very little of the Old Town is air-conditioned.