How to resolve error in AWS Route 53 - import zone file error : Multiple Distinct TTL values?

I was getting the same error importing a zone file from DNSimple into Route 53. My problem was that I had multiple TXT records for the same domain, and those TXT records had different TTL values. In Route 53, records of the same type (TXT, MX, CNAME, etc) for the same domain or subdomain get grouped together in a "record set" with one TTL value, so my zone file was breaking it. As soon as I changed them all to the same TTL, the zone file could be imported.

I went through the zone file by eliminating sections and trying to import it. Finally figured out the section that was giving me the grief. The MX records shown below are exactly as imported from Linode.

@       3600    MX  1   ASPMX.L.GOOGLE.COM.
@       3600    MX  5   ALT1.ASPMX.L.GOOGLE.COM.
@           MX  5   ALT2.ASPMX.L.GOOGLE.COM.
@           MX  10  ASPMX2.GOOGLEMAIL.COM.
@           MX  10  ASPMX3.GOOGLEMAIL.COM.

If I remove 3600 from the first two lines, I was able to import the file. Not sure why Linode gives out this file. So MX records now look like this when I import them.

@           MX  1   ASPMX.L.GOOGLE.COM.
@           MX  5   ALT1.ASPMX.L.GOOGLE.COM.
@           MX  5   ALT2.ASPMX.L.GOOGLE.COM.
@           MX  10  ASPMX2.GOOGLEMAIL.COM.
@           MX  10  ASPMX3.GOOGLEMAIL.COM.