Is diltiazem hcl 240 mg cap the same as diltiazem hcl 240 mg er cd cap?

It is the same: drug/medication but the ER indicates the second pill is extended release. This formulation would allow the same 240 mg to be slowly released over the course of a day; one would only need to take it once a day. In the first pill, the 240 mg would need to be spread out over the day, typically 60 mg four times a day (every 6 hours). Most prefer the once a day formulation. Stay well:)