most dedicated macro lenses are prime lens hence no zoom.
Zooming is just to get the far subject to fill your frame but magnification is to shoot somthing at real close distant so that the subject looks bigger in your viewfinder, just like your magnifier glass. Take your magnifier glass and check it out.
Magnification is an interesting concept. Imagine if you have a 5:1 mag ratio, you can shoot
a 0.7xo.46cm square on your 35mm film. When printed on a 12:8" paper, it will be additional
8.7 magnification. Now you effectively amplified a subject by 43.5 times.
The only difference is that in the case of a normal lens, you'll hit a limit that you can't zoom in anymore. For normal lenses, you can't zoom until this close as shown. Apologies for bad example but the below is still not 1:1.
As for the "magnification", it's just a constant terminology that people use similar to micro-scope where they say can magnify 50x, 100x etc. 1x simply means 1mm translate to 1mm on cam sensor and 5x means the image would be 5mm on your sensor.
Of course in photography when you print, there's also enlargement from your sensor size to printsize.
R u using a Digital SLR? If yes, remove your lens. See the sensor (with curtain opened of course)? Now, at 1:1, an object 1cm in length will be 1 cm physically on your sensor. So as to say if your sensor is 2 cm in length, a 1cm object will cover half your sensor, thus will 1/2 of your final pic. So if u r wondering how an ant will appear at 1:1, just imagine it crawing on your sensor, thats about how big it can go at 1:1.