Ronaldo cut into the area from the left before curling a spectacular effort into the top corner in a 2-1 Trofeo Santiago Bernabeu win on Wednesday.
The Portuguese star is banned from competitive domestic action for another three games after being sent off, and then pushing the referee, in the first leg of the Supercopa de Espana against Barcelona earlier this month.
Zidane said Ronaldo's goal against Fiorentina was exactly what the 32-year-old could do, as he praised his team's performance.
"That's what this man is capable of, we're happy to have him here," the Frenchman told Real Madrid TV.
"We put in a disciplined display and made a good start. I'm happy because the fans came out in their numbers and that was very important for us.
"We achieved what we wanted to, the trophy remains here and we all head home happy."
Zidane said he was pleased to get the opportunity to give some of his players, Ronaldo among them, much-needed game time.
Madrid have opened their campaign by winning the UEFA Super Cup, Supercopa de Espana and first LaLiga outing.
"We got what we were hoping for, gave those players who hadn't had much of a chance some minutes and that's what these games are for," Zidane said.
"[Dani] Ceballos, Marcos [Llorente], Borja [Mayoral], Cristiano all got some game time.