Extract parts of a string using head and tail only

Hello I would like to know if there is a way where I can only use head, tail, and pipes (and redirection eventually) to extract and output the start, middle characters, and end of a string Example: Given this string: SHOWpijfirefjTHISezpijSTRING, the command should output 'SHOWTHISSTRING' I tried something like (head -c 4 mdp > /dev/tty) | (tail -c +13 mdp | head -c 4 > /dev/tty) | (tail -c 6 mdp > /dev/tty) 2>&1 but it doesn't always return the same result and can give out of order results