Okay it's not a PRSA so it's legal for a charge to be applied to your transfer. That's just the strict legal position. Whether or not you should have been told about such a charge before the transfer happened is another matter entirely. Again from a purely legal point of view, commission disclosure regulations don't apply to Occupational Pension Schemes so from what you've posted, nothing illegal has been done here. (Don't shoot the messenger - personally I think that charges and commissions should have been disclosed to you as they've come out of your fund, regardless of whether or not it was an obligation. I'm just letting you know what the rules say.)
There is definitely a few questions to answer as to what happened to your funds between when they were cashed out of Zurich Life in November 2017 and when they were invested in Aviva in March 2018. Why did it take so long and where were the funds in the interim period.
If the broker was the one proposing this transfer and dealing with it, then it's the broker company you should go back to in the first instance.
Strictly speaking, the client in this instance is the company - your employer - and not you. So the broker might not discuss this with you for that reason. Are you a director or senior manager of the company yourself? If so, you can contact the broker on behalf of the company. Otherwise you'll need to talk to someone within the company, e.g. a HR manager or Finance Director and get them to contact the broker with your queries.