While Microsoft gives nice documentation (https://technet.microsoft.com/en-us/library/jj649911.aspx) for Set-DnsServerResourceRecord and Get-DnsServerResourceRecord, there is no example on howto make changes on all records at once. Here is simple PS script for changing TTL on all A records in DNS Zone.

$TTL = [System.TimeSpan]::FromHours(12)
$ZoneName = "lazic.info"
$Zone = Get-DnsServerResourceRecord -ZoneName $ZoneName -RRType "A"
foreach ($Record in $Zone) {
$New = $Old = $Record;
$New.TimeToLive = $TTL;
Set-DnsServerResourceRecord -NewInputObject $New -OldInputObject $Old -ZoneName $ZoneName -PassThru
}