QBasic, 151 122 bytes
Really just for fun (via QB64) - it doesn't golf well
Taking some ABS()
inspiration from Joffan's VBA answer but applying it differently:
FOR i=-25 TO 25
FOR n=0 TO 25-abs(i)
s$=s$+chr$(n+65)
IF n THEN t$=t$+chr$(90-abs(i)-abs(n))
NEXT
? s$+t$
s$=""
t$=""
NEXT
Previously:
FOR i=0 TO 25
p(i)
NEXT
FOR i=0 to 25
p(25-i)
NEXT
SUB p(i)
FOR n=0 TO i
s$=s$+chr$(n+65)
IF n THEN t$=t$+chr$(65+i-n)
NEXT
? s$+t$
s$=""
t$=""
END SUB