If you want your relationship with Amex to grow you will have to cancel that $500 Zync. Your member date will always be the year of your first card so no worries there, just keep a record of the number so you can get any future accounts backdated.
What's in my wallet: Cap1 Venture NFCU Sig Visa Delta Gold Amex BCE Citi Simplicity IHG World MC Amazon Visa CSP
Starting Score: 5/2010 550-ish
Current Score: 6/20/2013 TU 800 6/20/2013 EQ 770 6/20/2013 EX 775
Goal Score: 800 accross the board