When I put the phone on to charge, if I try and use it it keeps zooming in.
Your description is very limited. But I have seen problematic touchscreen behavior with my old FP2 when I used certain chargers. Mostly, the screen did not react any more at all in my case. This might be similar, likely caused by some sort of EM distortion of the charger - possibly in combination with other nearby devices. If you have multiple chargers, you may want to try those out. You could also try different charging locations to hopefully get a better picture of the issue.
(Before anyone joins in about “gounding” issues: Neither the standard chargers nor the secondary (output) side have any real connection to your house’s (or wherever you charge) electrical ground.