How can Newton's first law be derived from Newton's second law?

1st Law states that an object will continue without a change in motion (constant velocity) if there are no outside forces.
2nd Law states that to have an there must be an outside force.
##sumF=m*a##
If F = 0
##sumF=m*a## becomes
##0=m*a##
##0=a##
And if there is no acceleration there is no change in motion (1st law).