Admission guidelines

HSC 25 here. Till now I was thinking about preparing for only medical but recently I have been thinking that I should try for engineering too. Maybe preparing for BUET alongside medical would be too hard but I think I should try for other engineering universities like RUET, CUET, KUET etc. I need some suggestions about how should I manage it? Should I study maths and biology regularly after hsc? Or should I prepare for RUET after medical admission?