Online teaching and learning became the everyday practice during the Covid-19 pandemic in education, worldwide. There is a strong belief that this is going to be part of the common practice even in the post-pandemic times. So it is important to systematically measure the user experience from the perspective of key stakeholders. In this paper, we report findings of a large scale multi-faceted usability evaluation study of the most widely used tools for synchronous online teaching and learning (Zoom vs competitors). The study was conducted by three independent groups of experts. They performed a comparative evaluation of Zoom to competing other online synchronous teaching/learning environments and triangulated the findings of the study, using alternative evaluation methods (personas, heuristics, interviews, etc.). The objective of the study was to show that using standard usability evaluation methods we can identify flows in the design of the evaluated tools. In particular, the study highlights common findings of the three evaluation studies and produces a list of suggestions of improvements of this widely used online teaching/learning platform, while we discuss the contribution of different evaluation methods in the final recommendations.