How to keyframe zoompan filter in ffmpeg?
With loop added, you are generating a video stream from the image. Now, zoom is applicable within the processing loop of a single frame, and pzoom for video streams. Also, zoompan doesn't have timeline editing support, no enable won't work. So,

ffmpeg -i $FOOTAGE -loop 1 -i $IMAGE -filter_complex \
"
[1:v]
 zoompan=
    z='if(gte(in,24),min(pzoom+1.3/18,2.3),19.3/18)'
    :x='iw/2-(iw/pzoom/2)'
    :y='ih/2-(ih/pzoom/2)'
    :d=1
    :s=500x100
[name];
[0:v][name]
  overlay=
    x=1005-250-3*n
    :y=406-50
    :enable='lte(n,173)'
" -t 7 -y  -hide_banner  out.mp4