Where on “Como” are you starting? And what day? Looks like the Lyon concert is June 2 and 3d, is that correct? What day do you want to travel? There are some differences between travel on May 31 (Friday) and June 1 (Saturday) due to construction planned on June 1.
You can see the routes and buy the tickets for the whole journey as one ticket on SBB.ch
For 31 May, If you are starting in the town of Como, then SBB is showing the best route (meaning simplest and fastest) as Como S.Giovanni—-Zurich—-Dijon—-Lyon, 3 changes, total journey time 8 h 6 minutes.
However, there is a scheduled interruption in service on this route June 1, so you would bbe better off with the route via Milan and Geneva. If you depart at 10:10, This takes 8 h 43 min and has 4 changes on the way. You cannot buy the whole route on SBB. However, if you wait til 12:10 to depart, you can take a direct train from Geneva to Lyon, and buy the whole thing on SBB.
If you are starting in Varenna, you use the Milan—Geneva route.
All of these have different prices, depending on the date and route chosen. So you will need to compare the options.