扎实 (zhā shi): แข็งแรง

He studied very solidly during university; not only did he master textbook knowledge, but he also actively participated in research projects.

The foundation of this building is very solid, so it can withstand an magnitude 8 earthquake.

To prepare for this speech, she consulted a large amount of material, and the content was very solid.

Although he has worked for many years, he still maintains solid basic skills and practices every day.

This team's professional knowledge is very solid, so clients trust their proposals very much.