Nope.You'll blow both amps or at least the one.

Get a SIMA or Niles speaker selector box with impedence magnification.

A line/tape out running to a line/tape in will work fine. For secondary speakers, there are no particular requirements either unit needs to match other than buying sufficient power to drive the attached set of speakers.

Running speaker outs to a line in will not work well, which is what I think the previous post is meant to imply though that won't blow the amplifier(s). Connecting two amplifier's speaker outputs together will probably blow up something - if not everything.

Unless you are just hot to buy a second amplifier and volume control, I would look into a speaker switch box. Depending on your amplifier and speakers, there is very likely no reason you cannot use a simple switch to add your additional speakers. You should decide how many sets will be playing at any one time and whether you need volume control over each set.

If your amplifier switches A-B speakers by placing the sets in parallel (most amplifiers with A-B switching operate this way), you should look for a switch box with some form of load protection. This can be as simple as a load/power resistor switched in line or as sophisticated as an autoformer which will then show a constant, nominal load impedance to your amplifier no matter how many speakers are playing at one time. The latter is the preferred method but the former is far less expensive. Should your amplifier switch A-B speakers by connecting them in series, as all original Sony and early Kenwood/Trio receivers and amplfiers did until the late 1970's, you can use a simple switch box with no real problems other than a dimishing power output from the amplifier as more speakers are added. A series connected A-B should still only be expected to drive three pair of eight Ohm nominal speakers without problems.

Decide what your future needs might require before making a purchase. Buy a switch box with expansion possibilites in mind. Speaker selectors can have individual volume controls for each pair of speakers included at the switch box or you can place volume controls at each speaker location. Which you choose is a matter of convenience and the wiring layout in your home. Niles, Russound and several other companies make good speaker switches. Put "speaker selector/switch box" into a search engine to do your research and then call your local dealer for a finanl recommendation. Also, place "impedance matching" into a search engine for information regarding autoformer type switch boxes.